Remember, there are 3 types of billing plans.
1. The Full Payment Plan: you just pay the full price one time and are never billed again.
2. The 3 Payment Plan: the full price was split into 3 monthly payments. You paid the FIRST payment when you placed your order. The SECOND payment will automatically bill exactly 30 days after your order. The THIRD payment will bill exactly 30 days after your second payment.
This should answer your question, but if you're still not clear please click any support link on this page to open a support ticket.