Never heard of that before to be honest with you.  However, every provider has her own methods of screening her clients.  This may just be part of her way of screening.  If she does call you, unless she blocks her number, it will show up on your phone.  

If I have to call a provider to let her know I'm on the way, or to get her room number, I generally tell her my number so she will know it's me calling.

Lou

I sent an email out to a provider who asked for my number to call me back- no number given on her part- is this a standard practice? Thanks.

I know two ladies for problems that have happened in the past request your number first, but this was after the date was set by email. They will, if its OK per email, call you first about an hour before to give you the general location, at which point you will have her number to call at arrival. It just to avoid giving their number out to no shows as much as possible. They then in the future allow you to use the number directly, it is just to weed out time wasters on the phone. They require email as first contact for anyone they have not screened. Also in a third case, she does not call you but only answers her phone for numbers she knows the number of the incoming call. If your using a hobby phone and have done your research, this should not be a problem as you will both know each others number before the session. I know of no lady who will answer a blocked number call.

I can only speak for myself but the easiest way to find out whether you are blacklisted anywhere is by using your phone number, hence the request. Some ladies who do less business and have more steady regulars just don't want their phone number on the internet and will only trust those who are pre-screened with that information.

Sometimes during screening I will ask for a phone number to further verify your identity if you do not have enough information/references, etc.

After you are scheduled for an appointment, I will give you my phone number and let you know that I will call you when on my way. I can only assume you have a "hobby phone" or have your phone situation in order. At no other time, other than for your appointment, do I call you. I actually make sure your phone number is out of my hobby phone until we schedule another date.

Have fun & Stay safe!

Summer
No Pm's/only email