it appears that you are signing up with a company and have a trainer assigned to you. This is how most companies (and individual trainers) do business as you have seen from the responses of my colleagues. I also ask for an initial pre-payment for a package of 3 sessions and an assessment. Payment is due for that when I first meet the client. My rationale is that an assessment is a lot of work to compile, and I want to protect myself from spending about 3 hours of my time for nothing. After that, though, I bill clients on a monthly basis for the number of sessions that they had with me. I have only one rate and do not give discounted packages.