bad service

Telkom kept the contract on pay as you go for months without my knowlegd , when i discover i then ask them to cancel the contract. However they kept on debiting my account and i reversed the payment. Now they send me to the attorneys to collected R1730,38 for the 2 days they claim I logged on to the data. How do i pay for something that i have already paid for. I spoke to more than 3 agents who didn't tell me that there was money outstanding. Not sure if this big companies can just get away with ***** from people.