SMS or WhatsApp for missed calls? How to choose

The short answer

If most of your customers already message businesses on WhatsApp, a WhatsApp text back will feel natural to them. If you're not sure, or your callers are a broad mix of people, start with SMS: it reaches any mobile phone, with nothing to install. Plenty of businesses end up using both.

The rest of this guide explains how each channel works when the trigger is a missed phone call, which is a different situation from a customer messaging you first.

How SMS text back works

With SMS, the text comes from your business number, or a number linked to it, and lands in the caller's normal messages app. Nobody needs an account or an app, and replies come straight back to you.

• Reach: any mobile phone.
• The first message: your own wording, within your provider's rules.
• Length: 160 characters per part with plain characters, or 70 if you use emoji or special punctuation.
• Setup: many countries require registration before businesses can text. In the US, local numbers need A2P 10DLC registration (opens in a new tab) and toll-free numbers need verification. In India, business SMS must be registered on the TRAI (opens in a new tab) DLT platform, sender name and message templates included.

Registration can take days or weeks, so start early. Unregistered business texts are often filtered or blocked.

How WhatsApp text back works

WhatsApp works differently, because a phone call doesn't open a WhatsApp conversation. To message someone who called you, a business uses the WhatsApp Business Platform through a provider, and the first message must be a template that Meta has reviewed and approved.

• Permission first. WhatsApp's Business Messaging Policy (opens in a new tab) requires that people have agreed to hear from you on WhatsApp before you message them.
• Templates for the first message. You write it in advance and submit it. Meta checks the wording and assigns a category, such as utility or marketing.
• A 24-hour window for replies. When the customer replies, you can answer in your own words for 24 hours after their last message. After that, you're back to templates.
• Costs. Meta charges for many template messages, at rates that vary by country and category, while replies inside the 24-hour window are generally free. Check Meta's pricing page (opens in a new tab) for current rates.
• Your business profile. Customers see your business name and profile, which helps them trust the message.

SMS and WhatsApp side by side

Rules that apply to both

• Message only the person who called, and only about their call.
• Say who you are straight away.
• Make opting out easy, and honour it at once.
• Keep marketing out of missed-call replies.
• Store conversations securely, and only for as long as you need them.

This isn't legal advice. Rules vary by country, so check with your provider and get local advice if you need it. Our complete guide covers consent and opt-outs in more detail.

How to choose: five questions

1. Do customers already message you on WhatsApp?

   If they do, WhatsApp will feel familiar. If nobody does, SMS is the safer start.

2. Who calls you?

   A broad mix of callers is easiest to reach by SMS. If many callers are abroad, WhatsApp can be simpler than texting internationally.

3. Can you get permission for WhatsApp?

   You need people's agreement to message them on WhatsApp. Think about where you'll ask for it, such as your website or booking form.

4. Is your registration done?

   SMS registration and WhatsApp template approval both take time. Whichever is ready first can go live first.

5. Will your team answer it?

   Both channels end the same way: a booking, a callback or a hand-off to a person. Pick the one your team will actually keep up with.

Dolittle runs on either channel. During setup we choose the one that fits your customers, and everything else works the same way: the first text, the questions, the booking and the brief for your team. For wording you can adapt to either channel, see our missed-call text templates.