Mejor respuesta
Collect the number inside the conversation with explicit consent, store it on the contact, and send from the SMS channel afterwards. The mechanics are simple; the consent is the part to get right.
The flow:
- Ask for the number at the point where it is obviously useful, such as a booking or a delivery update, not as a generic opt in.
- Say what you will send and how often, in one line, before they type it.
- Use a button they tap to confirm rather than treating a typed number as agreement.
- Store the number and a consent tag with the date.
- Send from a flow that filters on that tag, never on the whole contact list.
The rules are stricter than the DM rules and they come from telecoms regulators rather than Meta. Consent has to be specific and recorded, every message needs a way out, and STOP has to work immediately. Unlike Instagram, SMS has a real per message cost, so a badly targeted send is expensive as well as unwelcome.
One design note that saves money: SMS is the right channel for something time sensitive and short. If what you want to send is long or can wait, email is cheaper and better tolerated, and you can ask for both in the same conversation with separate consent for each.
The Connect SMS and Email article covers sender setup and the opt out handling.