More important that "how" restrictions are figured, you also have to remember that discussion of ANYTHING sexual on the phone can break the legal barrier between COMPANION and SOLICITING.
It is VERY unlikely that an agency will be really willing to discuss the issues on the phone. They will use nice generalities about how the girl is "open minded" and "flexible" about plans for your time together. If they are talking sex, they are breaking the law.
Be clean, be nice, be reasonable, and you will probably get the best the girl is willing to offer. Show up less than clean, be less than friendly, and be less than reasonable, and the girl will do the minimum required to keep you from bitching to her boss - but she sure won't be into it, won't enjoy it, and won't go 1 inch to make it any better.
You can basically count on the basics... CBJ, FS, 1SOG. After that, well... YMMV!