Monthly payments made on time, yet my balance is increasing not decreasing on statements!

My Edgars was handed over to them and Ive been paying them more than the minimum amount monthly without missing a payment. However on my statement that they email me every month my total balance keeps increasing! I would like to know why this is the case. I called in to customer services and requested an explanation and the lady could not give me a sensible explanation. Before I make any more payments I need to understand why my amount is not decreasing else I will be taking legal steps to investigate.