I do not believe that Global Courtesans is a reliable agency.  I know that some have had good experiences with them but I also know several porn stars who are listed on their site who never heard of them, and others that won't work with them.  TLC is the best, followed by Pam.  After that, I'd go with BodyMiracle or Lita.  Between those, and the independents, you're pretty well covered and there's no need to use a potentially unreliable agency like GC.

As for MyPlatinumProvider, who is supposedly another player in this game, I have my doubts.  Until their posting here a short time ago, I thought they were out of business.  I've tried to contact them for information on providers they've advertised and have not gotten an answer. I've filled in the form on their website to get access to the VIP list at least 3 times and have not gotten an answer.  I have tried to contact them to set up an appointment with one of their ladies and have not gotten an answer.  They have ladies listed on their site that I believe are not actually available. So, while other people seem to like them and use them, I have my doubts about them.

As for changing your username... contact support by clicking the "Contact Us" link at the bottom of the page.  They're the only ones who can help you with that.  However, if all you are seeking is anonymity on the boards, you might try using an alias.  If you pay for VIP or get VIP credits for posting reviews, you can use an alias when posting to the boards that hides your real id.  No one will be able to contact you through the alias though, and the reviews will have your real id.  But, at least it's better than nothing.