Cell C changed my contract and billed me an unagreed amount

I received a call from cell c to change my contract from Top up 100 to the pinnacle 100 as Cell C no longer provided the top up 100 service. I was offered a phone which I declined. I asked if all my services will stay the same and what the amount would be. The gentleman I formed me that because I didn't take the phone it would only cost me R129 per month to which I agreed. My account has since been debited with an amount of R1044.00. When I called to query I was informed that my fee was actually R329 odd and not the R129 I had agreed upon. furthermore they charged me an out of bundle data charge of R500. Again of which I did not agree too. I went from paying my original contract with a phone of R449 to two times the amount. This is totally unacceptable. I am still waiting for a manger to call me back and explain where the error happened. I would like this contract cancelled with immediate effect. having R1044 debited from your account when you are expecting a mere R129 is absurd and completely misleading!