Jack, a bit of safety is better than none.
If the buy book with a hobby phone and never show-up, the girl will remember the phone number and it's unlikely the guy will get a new phone for each encounter.
My carrier is Virgin Mobile. Apparently, I can change phone number at will. This can be done from the internet. No questions asked. No fee. No nothing. Supposedly, I can change number once a day, everyday, as long as I subscribe to the service.
I've never tried it though.
YoungBob