Are you emailing or calling?  Without knowing how you're approaching providers it's hard to comment. Are you asking for a specific day and time to meet? Are you asking to many questions? Lots of variables, but whatever you're doing it's not working so maybe you need to change your approach.  

I prefer email.  If I don't get a response I wait a day or two and then try again. If no reply to the second attempt, I simply move on.  

Not throwing stones but being able to communicate like an intelligent person will usually get you in the door.

Something like this usually works...

Hello,

Hope you a are doing well, my name is xxxxxx, I saw you're ad on TER, I must say the pictures really got my imagination spinning. I was wondering if you had any availability for next Monday afternoon, maybe around 4ish? I will be happy to supply my P411 info and references if you think we can get together.

Xxxxxx

Some guys and a lot of ladies prefer the P411 info in an initial request, I usually don't I like to get a bit of a gauge on her personality before meeting. So I use the extra email to help see if I think we may get along well. If her site specifically says to include that in the first contact then I will. Not a lot of ladies in my area so I tend to pull them in from little ways out, so usually I'm seeing if that's even an option before trying to nail down a date.

It's simple, be sincere, honest and write like you have a functioning brain. Don't let the little head do the thinking for ya, jueveille jokes and crude pick up lines will get you in the trash folder quicker than almost anything. No saying you're doing this but others may get some use from this.  

Have fun!!!

Unless they're idiotic or easily found (i.e. my rates, asking for more photos, overly explicit). But that's just how I was raised.

Not every provider is going to take the time to tell a guy that, so they just ignore you. Move on.