MTN SA - BREACH OF CONTRACT

I am literally at my wits end with this company. How is it possible for such a big corporation like this failing to solve a simple issue of identifying what happened to my data bundle since the 12th of April till now. I have been told that there is still an ongoing investigation - for over a month!! Not to mention the appalling rude treatment that I have been constantly receiving from the so called agents. Right now all that I want is to cancel my contract without fees because the company has failed me. Is it even legal in SA to force someone to stay on a contract that no longer serves them? Because that is what I have been told by one of the agents, that I cant cancel my contract. Basically I'm stuck with a contract that mtn has breached by not giving me what we agreed on. I feel sorry for anyone whose currently considering associating themselves with mtn.