Unauthorized subscription to extra internet

I lodged a query last month as telkom debited R500 extra for my internet service, they said they would investigate the problem and a few days later I get an ama saying they ha e concluded the investigation and no refunds will be made to the account.. I told them that I have not subscribed to the extra internet.. This month again the debited another R500 extra.. Someone at telkom is doing ******* activities with our accounts and they expect us to pay.. I refuse to pay for a service I did not subscribe to