Month to Month Contract turned to fixed term

I have been a client of Cell C for almost 5 years now and i am highly disappointed that i have now called them to cancel my data contract which is way beyond its 24 months contract and has been running on month to month basis, only to be told they extended it by 12 months without my consent and i therefore cannot cancel. I do not need this service anymore and I cannot afford to continue to pay this and what even frustrates me more is that I have to run up and down from department to department trying to get this cancelled which is also a costly exercise. This is pure ***** and I cannot rest until this is cancelled. Even worse i have a phone contract and i just want to settle it and move on to the next network.