I think the most likely reasons the provider is hanging up on you are that you are asking about things that are readily apparent on her ad/webpage, or you are being explicit and the provider thinks you're trying to get her to incriminate herself or are just looking for a free phone sex session.

Some providers, as part of their screening processes, will not accept calls from blocked phone numbers or numbers which are identifiable as coming from "burner" apps. YMMV but that is a possible explanation, too.

And the "bust" site that you're referring to is a scam.

It's requested on my website, and until I have it, I can't commit to dates or times anyway, so it's a waste of both our time to plan a hypothetical meet up.

I've actually taken my number off of my site because of so many calls like this.  

Most of my provider friends tell me that their favorite method of communication is email, and that people who call rather than email tend to be time wasters.

Any polite introduction email stating where you found me, when you'd like to meet, and including the screening info requested on my site (ideally two references), will be answered immediately.  
Anything less goes to the back of my to-do list.  

Make it easy for your provider and she'll be excited to meet you! How you introduce yourself says heaps about what kind of date you'll be

All good providers do not have time to discuss availability/schedule over phone so email/text is the best way to communicate. Be polite, short and specific when communicating as all good providers truly deserve that. Enough Said!