Change account details before buying extension



I have a wrong name and an incorrect email address in my account details. I opened a forum together with a friend years ago, he was looking after xenforo at that time. He got out and I went on. Now I face the problem that his name is still registered, but I need an invoice later on my name (tax authority).

How can I change the name and e-mail address? I do not want to extend it to a wrong name again.

Hopefully there is a solution for that.