Glossary
What is Opt-out?
An opt-out is a person's request to stop getting texts from a business, and the business's record of it, so nothing more goes to that number.
PECR requires every marketing text to offer a simple way to opt out, free apart from the cost of sending a reply, and in practice that usually means 'Reply STOP'. The ICO says you should act on opt-outs promptly and keep a suppression list (a do-not-contact list) to check before sending marketing. People don't always use the keyword, though. Someone might email, or tell you at the counter, and you should honour that just the same.
If a customer of a Brighton bike shop rings up and says 'please stop the texts', the shop should add the number to its list there and then, without waiting for them to reply STOP.
Every CaptiFi Connect account has an opt-out list. STOP and the other keywords add a number automatically, START or UNSTOP takes it off, and you can add or remove numbers by hand. Any text to a listed number is refused with a reason and costs nothing, and texts already scheduled to it are cancelled and refunded.