Phone numbers are of little importance in my opinion. I prefer to monitor profiles in my hotlist for a while, look at how frequently they log in, build up feedback etc.
I usually plan my punts in advance so am happy to exchange a few messages on AW in the days before, then you get a feel for what sort of girl you're dealing with.
It's a little disconcerting if you make a booking and they still don't give out a number or make contact on the day, but so far I've found the girls who insist on only communicating through AW messages to be reliable.