That seems a bit overkill to me 😉
If a new member sends his phone nimber for discussing further questions or asks for mine, I just say, that phone bumbers are censored before the booking is completed.
I refuse all messenger apps after booking too, sms limited to emergency situations.
If they ask for the phone number to discuss alternative payment methods, obviously knowing, what they do, I would not waste time sending help files, but flag them to trust and security. If their first request is to help them fraud m'y longterm business partner out of his commission, I don't want them in my house anyway.