OTP via SMS vs WhatsApp vs Voice Call: Which Is the Best 2FA Method for Your Business?

June 22, 2026

With the average cost of a data breach hitting $5.3M in 2025; a 12% jump from the year before (Avatier, 2025), 2FA is no longer optional. We believe that businesses that skip it are playing with fire. However, not all 2FA is created equal, the difference becomes obvious the moment you compare two-factor authentication SMS vs WhatsApp options against your own customer base.

The three most common OTP delivery channels i.e. SMS, Whatsapp and Voice call; each carry a set of trade-offs around security, delivery reliability, cost and user experience. Therefore, using the wrong one for your business can mean failed logins, abandoned transactions, penalties or worse…a breach. Finding the best OTP method for business Pakistan teams can rely on isn’t about picking a single one-time password channel and sticking with it forever, it’s about matching each channel to the right use case.

This guide breaks down all three with real data, regulatory context, and a clear recommendation based on your use case.

At ITS, we help businesses across Pakistan put together 2FA for business customers actually trust, combining short code SMS , WhatsApp OTAC service in Pakistan users already rely on, and Voice OTP under a single platform. Because the right balance of OTP delivery rate, cost and customer verification needs changes from one industry to the next, ITS works with you to build account security messaging that protects login without adding friction.

Why OTP Channel Choice Matters More Than You Think

According to a 2023 study by Vonage, 67% of users would be so frustrated by the delay of an OTP (Within 30 seconds) that they would abandon a transaction (MessageCentral, 2025). That isn’t a security issue – that is a revenue issue.

Meanwhile the regulatory landscape is rapidly evolving. In December 2024, the FBI and CISA issued a shared warning to organizations to avoid SMS authentication due to the Salt Typhoon cyberattacks which targeted several U.S. telecom providers. NIST’s new SP 800-63-4 standard defines SMS as an “authenticator” that requires a formal risk assessment process before federal agencies should continue to use it (Security Boulevard, 2026).

The stakes are real. Here’s what the data says about each channel, and how it affects login verification for the people relying on it.

OTP via SMS

How It Works

A short number is sent to the user’s telephone number through the cellular carrier network. No internet connection required. Works on any cell phone, smartphone or basic feature phone.

Adoption & Scale

• 41% of users currently rely on SMS-based verification, making it the most widely used 2FA method (Electroiq, 2025)
• SMS can reach 5.1 billion users globally, roughly 67% of the world’s population on any mobile device (Sendwo, 2025)
• Juniper Research estimates SMS OTP traffic will reach 1.5 trillion messages by 2028, up from ~1.3 trillion in 2023

Delivery & Speed

• The delivery rate is 94-98% post compliance in regulated markets and is reduced to ~85% in high-DND environments such as India (MessageCentral, 2025; Fyno, 2024)
• Usual delivery time: 5-7 seconds with normal network environment; 5-30 seconds under the condition of network congestion.
• Average delivery time is 3 minutes – 98-99% open rate (Sendwo, 2025).

Security

This is where SMS has a serious and growing problem.

• SIM swap fraud: The UK’s fraud watchdog Cifas noted that there had been a 1,055% increase in the number of unauthorized SIM swaps in 2024 from 289 to almost 3,000. The FBI’s Internet Crime Complaint Center reported a total loss of $26 million due to SIM swapping in the US in 2024 (iProov, 2026)
• SMS weaknesses: The decades-old 2G/3G network signaling protocol (SS7) has design flaws that could enable an advanced hacker to intercept SMS messages, such as OTPs, while they are in transit.
• FBI losses: The FBI reported over $320 million in losses from SIM swap fraud in 2024 (Dexatel, 2025)

It is widely used today because SMS 2FA is able to block 100% of automated attacks and 96% of bulk phishing attacks when used correctly, according to Google’s research (Notifyre, 2026).

Regulatory Pressure

SMS OTP Regulatory Timeline: 2024–2026

Cost

• $0.01–$0.15 per message, depending on carrier route quality and destination country (Dexatel, 2025)

Best For

• Maximum geographic reach, including rural and low-connectivity areas
• Users on feature phones or basic devices
• Fallback channel when primary delivery fails
• Low-risk authentication scenarios (not financial transactions in regulated markets)

In Pakistan, ITS delivers short code SMS Pakistan businesses rely on for fast, carrier-grade one-time password verification, with automatic fallback to WhatsApp or Voice when SMS delivery rate dips in high-DND environments.

OTP via WhatsApp

How It Works

• Using the WhatsApp Business API, businesses send OTPs through pre-approved message templates.
• The code is sent via internet connection, using end-to-end encryption, to the user’s WhatsApp application.

Adoption & Scale

• This means that as of 2026, WhatsApp is used by 2.7 billion people worldwide (ChatMaxima, 2026).
• The SMS delivery is not always reliable in the following areas; Dominant channel in South Asia, Southeast Asia, Latin America and the Middle East

Delivery & Speed

• The delivery time is less than two seconds on active Internet connections (ChatMaxima, 2026).
• High delivery rate: 95-98%, which exceeds the delivery rate of SMS in markets with high WhatsApp penetration (Dexatel, 2026).
• In optimal conditions, the rate of WhatsApp OTP delivery in emerging markets is ~99.5% (Dexatel, 2026).
• Open rates: 90–95% within 3 minutes, versus ~70–80% for SMS (ChatMaxima, 2026)
• In one instance, a business that reduced SMS to secondary, using WhatsApp OTP as primary, experienced a 6% increase in OTP delivery rate and a 34% decrease in its “OTP not received” support tickets (Dexatel, 2026).

Security

• By default end-to-end encryption, unlike SMS, which cannot be intercepted in transit using SS7 attacks.
• Not susceptible to SIM swap as it is sent via Internet and not the carrier network.
• Less likely to be filtered as spam than SMS
• Contains read receipts,  businesses can know if OTPs have been delivered and read

Limitation: Vulnerable to phishing if a person is fooled into providing a code on an impersonated site. No form of OTP-based 2FA is resistant to an adversary in the middle and proxy attack.

Cost

• Costs of $0.005–$0.09 per message for the WhatsApp Business API , typically 50–90% lower than comparable SMS rates for foreign markets (Dexatel, 2025).
• The authentication pricing changes for July 2025 reduced the costs of WhatsApp OTPs by as much as 97.4% in certain markets (Dexatel 2026).

Limitations

• Needs internet connection, not suitable for users without a Wi-Fi or cell connection
• The user needs to have WhatsApp installed (not universal, particularly with the elderly and in areas outside of where WhatsApp is a key player)
• Authentication Message templates must be approved (setup time only, no ongoing monetary cost) by Meta before they can be used.
• Not a regulatory replacement in every market – ensure local compliance requirements are met

Best For

• Firms that have mobile apps that serve the majority of their customer base in WhatsApp-dominant markets.
• SMS companies wanting to save on SMS rates for bulk volumes
• Markets where SMS delivery is unreliable, but there is a high demand for delivery rates.
• Brands looking for a more robust and trusted authentication experience

ITS’ WhatsApp OTAC service Pakistan businesses use sends authenticated codes over a pre-approved Business API template, giving customer verification a faster and cheaper path than SMS alone,  without sacrificing account security messaging standards.

OTP via Voice Call

How It Works

An automated system dials the caller’s telephone number and then reads out the OTP (usually 2-3 times). The user listens and types in the code. Functioning on Smartphones and Landlines, with or without Internet.

Delivery & Speed

• According to a Twilio 2024 analysis, Voice OTP delivered a success rate of 98% in emerging markets, compared to SMS OTP which had a success rate of 92% (Africala, 2026).
• Voice calls have high priority in the network compared to data packets, ensuring more consistent delivery when network load is high
• Typical delivery: 15-30 seconds (including ring time) – faster than SMS, but still much slower than WhatsApp and works much better in low signal areas.

Security

• More resistant than SMS, access to the real-time call is needed to intercept the OTP (Dexatel, 2025)
• The OTP is a transient, it’s spoken once (or twice) only and will not be stored as a readable text message on the device.
• Less secure than WhatsApp,  voice calls are still vulnerable to social engineering or call forward attacks
• Not immune to vishing, attackers can call the users and pretend to be a support agent to get codes while it is being dialed.

Cost

• $0.02 – $0.25 per call depending on call length and geographic location (Dexatel, 2025)
• Most costly of the three channels, but is appropriate for high-value transaction verification.

Real-World Impact

• Asian Banking Association analysis (via Africala 2026) showed that in the first 6 months of implementing Voice OTP in its mobile banking app, one of the largest banks in Southeast Asia experienced a 30% decline in fraud cases.
• Africala, 2026, adds that an international e-commerce website reported a 15% rise in successful transactions following the deployment of Voice OTP as a standalone option when SMS fails.

Accessibility Advantages

Voice OTP is the only channel that fits these customers:

• Users who have difficulty seeing an SMS code
• Low-literacy users in emerging markets
• Customers who are using fixed-line telephones (businesses and older people)
• Users in locations with poor data reception but voice reception available.

Best For

• Financial transactions with higher value that need more confirmation
• Accessibility-first deployments
• If SMS delivery fails, fall back to another workflow.If SMS delivery fails, fall back to another workflow.
• Enterprise, banking and legacy or landline systems in the healthcare environment.

ITS rounds out the channel mix with Voice OTP for Pakistani businesses that need a reliable fallback for login verification when SMS and WhatsApp aren’t an option — covering landline customers, low-connectivity areas and high-value transactions alike.

Frequently Asked Questions

Will SMS OTP be safe in 2026?

Yes – SMS 2FA is a very effective solution for the majority of use cases. But it’s no longer adequate for high assurance applications, such as financial transactions. CISA, FBI, and the NIST have all issued guidance that SMS is not a reliable 2FA mechanism and several central banks have started the process of phasing it out for regulated financial services. While SMS for general consumers is still a viable method, for regulated businesses, that should be on the move.

So, the actual difference between SMS vs. WhatsApp OTP?

When used on a larger scale, WhatsApp can cost up to 50–90% less than SMS services on an international level. Some markets experienced drops of up to 97.4% per message due to WhatsApp’s July 2025 authentication pricing announcement. With businesses sending more than 100,000 OTPs per month, even a fraction of a cent per message can add up to a significant cost. However, the difference is quite significant in markets with low carrier rates for SMS messages.

Are there any templates that need to be used for WhatsApp OTPs?

Yes. Businesses need to make use of pre-approved authentication message templates via a registered Business Solution Provider, using the WhatsApp Business API. Approval of templates is usually a non-cost process that is one-time and involves no cost. The templates can be reused at scale once they’ve been approved.

Is it possible to completely replace SMS with Voice OTP?

No – Voice OTP is slower, more expensive and cumbersome in public spaces where users cannot make phone calls. It is most beneficial when SMS fails, for high-value transactions and as an alternative to SMS for users who cannot or will not use SMS.

Bottom Line

SMS-only OTP is not a thing of the past, it just never worked,  it’s no longer a threat that has been faced, it’s a threat that regulations have addressed. The road for the majority of businesses is:

Use WhatsApp OTP as the primary method, the faster, cheaper and safer option. SMS as fallback – universal reach and no internet users. Voice OTP for high value or accessibility scenarios – as an adjunct channel or niche solution. The right mix is dependent on your industry, geographical location, user base and regulatory requirements. No matter which you select, and the facts are quite clear – a botched or delayed OTP will cost more than a better channel.

For most businesses weighing 2FA for business Pakistan customers will accept, that means leaning on a provider that already runs all three channels under one roof. ITS gives you short code SMS Pakistan, WhatsApp OTAC and Voice OTP from a single dashboard, so you can route OTP delivery rate, cost and customer verification needs by use case instead of standing up three separate vendors.