Listen, this is what you need to do.

Write up a page listing exactly what you want, how you want it to work.
Be very detailed and precise.

Do you have already, a billing system?
A truppen tool system?
Do the above need to be made?
To what advantage does the user have to control there PHPBB account?
What can they do with it?
When they log in, what else can they do besides managing there PHPBB account (what account? where?), controlling their billing (billing for what?), their truppen tool account (what is truppen?)?
Are you want people to be able to control their accounts of other systems through one site?
What is it exactly that you want users to do and why?

These are just some of the 101 questions that you should tell us briefly, I mean, if I built you something from what you've said so far, it might turn out to be no where near what you are wanting.

You must explain!