Canselation of Contract

I had a contract with Cell C for 2 years and transferred it to my name March and upgraded it. Payment went of every month but in July it went of almost double, From the transfer and upgrade I am not getting my Value of what I signed for. From August 1st I have trying to cancel this contract, but They cant even find my Signed Copy in archives, There are just no progress with. month end is around the corner and then they want my money again. I want this contract cancel before month end. You can speak to customer care because they transfer you like 5-8 time just to speak to someone. I made Arrangement to give the devise back to Cell c to cancel the contract and they just have stories the whole time waiting for the contact. I want to take it further because Cell c gives the worst service ever and are busy to ******** me. Please can you assist