Payment plan

I made  a  50$ payment to start a payment plan. Changed the service to the 29.99$ / month option. Paid the 50$. Now it is telling me i need to pay the remainder of the balance. Why would i do that when i just changed my plan, put a down payment, and started on a plan that i will be paying 11$ a month for? When i call it is asking if i want to start a payment plan. That’s what i did already.