Streamline Aha! Billing

Use Case: When an existing account holder of Aha! (Roadmaps and Develop), every time I add seats to include more Develop engineers on board, Aha! allows the addition but emails an invoice. Why can't the client choose the preference to pay Aha! in the tool versus dealing with an emailed invoice? Why can't we choose to pay with a credit card from the billing section of Aha!?