When someone calls a NA helpline using yap, they have the option to receive meeting information via SMS text. This page describes how they opt in to receive this information.

Callers first hear a greeting “Washington Northern Idaho Region of Narcotics Anonymous. Press 1 to find someone to talk to, press 2 to search for meetings.” (This is for the Washington Northern Idaho Region helpline; there would be a different service body name read out for a different helpline.) If they press 1, the system attempts to locate a volunteer, and if found, connects the call. There is no SMS sent to the caller in that case. If they press 2, they are informed that if they want to continue, they will receive a text back with the meeting search results, and are given an opportunity to opt in to do so. The specific prompt they hear is “Meeting search results are also sent back by SMS text message. Press 1 to search for meetings by city, press 2 to search for meetings by zip code”. If they hang up at this point, no SMS is sent. If they opt in by pressing 1 or 2, and then provide a city or zip code, the system will read back the resulting meetings found, and also text them the result. The only SMS we send to callers is in immediate response to their explicit request for meeting information. The system doesn’t send them texts after the one response.

The fact that they consented to receive an SMS text and the time consent was given is recorded in the log for this call, as shown in this screenshot.