Billing

I have been calling and given the run around: I signed up last year and quickly found out I was being improperly billed and made a change in August 2014 to pay 77.53 a month. I have a copy of the contract. I checked my bills last month and found out your are billing me at 98.11 a month since august 2014- I'm wanting a credit or repayment for over billing. I cant reached that department. Please call me agreement number 165102322. Your phone customer service agents agree the billing was not right but don't have authority to repay me. help