Worst service when you have to cancel your contract and the end of the term

I have been calling MTN for over an hour trying to cancel my cellphone contract and i have been having the worst experience as both times when i mentioned that i want to cancel my contract the lady on the other side just immediately hangs up the call on me after being on the phone for over half an hour for both calls. It was so easy to open this contract and i have never defaulted and now i feel trapped as i am being refused a way out. It should not be this difficult just to exercise my right as a consumer to cancel my contract at the end of the 24 month contract period.