Never had a problem with them. Have to think you are doing something wrong.
Try something like this:
"Hi, is __________ available, please?"
(response about when the girl is available)
"Thanks! Could I please book for (however long) at (whatever time) please?"
(address follows)
"Thanks, I'm on my way."
Changing burner phone is a good idea as well, if you're already blacklisted, and don't block your phone or use some texting app if you want a response. They want to see who they are dealing with.
That should do it. Service standards are pretty consistent with them, and relevant info is generally in their ad, so don't waste their time with redundancies (eg "is kissing allowed?" or "are the pics legit?")
It seems they're big enough now that they really don't care if you book or not, because they're fully booked regardless. I remember when I was younger, we'd order after hours beer delivery from the boys, and if you even asked the price they'd just hang up on you. Think of them on those terms; it's likely similar folk running the place at the end of the day.