Unsubscribe from Texts

Hey there,

Occasionally, we get a repeat seller into the store whose phone number has changed.  When this happens, we send the "buy complete" text to a wrong number. 

Ideally, when this happens, we text a quick apology, go into DRS and delete their phone number so that we can get the right one when they come in next.  However, sometimes this is forgotten in our store.

Is there a way for people to opt out of texts via a text reply?  Perhaps there is another solution I'm missing?  Apart from better training ;)