@aaronpk Ugh, that's no fun. I stopped giving out a phone number for just this reason — instead I used an email address with an auto-reply that gave some T&Cs for purchasing from me.
It also worked as a form of reassurance — "by using email, we both have a written record of what we agreed to, which protects both of us!"
@AngeloStavrow yeah, for high value things I would do this too, but in this case I want this thing gone and I'm giving it away for free, on the condition that the buyer comes and picks it up. That means I need to make it as easy as possible for someone to contact me and not jump through hoops.