Several thing and I will try to keep it short.
If you want more information or something feel free to ask.
avast doesn't conflict with Vista.
The "customer service" you called is not avast but a call center that only handle certain things for avast.
They are not allowed (legally) to create a new account for you.
They don't and are not allowed to handle refund request.
Did you create a ticket at avast ?
If so, what is the ticket ID and on what date did you create it?
On a note,
the ticket system is a FiFo system.
Each time you submit a new ticket, you will be put back at the bottom of the stack.
