Telkom contract

I have a cellphone contract with telkom. My contract has been going well since one day u received an sms from them informing me that my account is near a credit limit and I should call them immediately. My monthly payment on my contract is R936. When I contacted them I was told that I have a subscription of R799 which I know nothing about. I tried to explain to them that I don't know any subscription and I never signed up for anything extra on my contract. I also asked them to cancel it and they told me it was canceled. I was informed that I will still be liable for the money for that month. The money was debited together with my initial contract payment and I accepted it.

What bothered me was that the next month they carried on debiting the money even after I asked them to cancel it. I feel like it's very much unfair what they are doing to me. And the problem is that I can't get out of contract because I still have 23 months before the contract ends. And I can't move my funds from my account because that will affect my credit score. I called several times to telkom but I don't get any help. I feel like I'm stuck in a situation where I can't get out of. I'm being treated unfairly and that hurts.