Flexible Billings Schedule Billings Invoices

Dear Experts-

Hi.  I have a client that is need to schedule multiple billings to multiple account categories under Flexible Billings.  I'm only able to create 1 schedule per 1 account category.  When I create multiple schedules it creates multiple invoices.  I only want one invoice with all of the account categories.  Can you think of any work arounds?

Thanks!

Serena