Bad service at vodacom

I have from I can remember a cellphone contract with vodacom. For the last two years my phone was more in for repairs then I had it by me. Now the phone has broken again and I don't have a spare phone to use. Their sevice is some times a whole day off in our district and my phone and home internet is almost permantly in a sos. They told me that I can upgrade on the 10th of march and if I want to cancel the contract I must pay my 4 months in advance or I must wait 4 months for it to be canceled. I want to change to mtn because of the sevice that is poor at vodacom and that they do not put enought effort in to give u back the value your money. What does it help I have internet at hom and a cellphone and I can't use it? I'm going to pay the money in advance so that I can get it over with. I'm very dissapionted because now I must pay money for their poor sevice.