Sick and Tired

First, we changed our contracts limit to 0.01c, and one month later I had to pay R 400 just to get the lines on (in which the lady told us that the fault is with MTN. We never received an SMS saying that our lines were suspended, I found it out after difficulty trying to figure out why my phone calls are not going through. What would've happened if there was an emergency? Then after that my phone fell (which was on insurance at MTN) and when I wanted to claim for it, they said I will have to pay an amount when booking in the phone, and thereafter i will receive an invoice with the total of fixing the phone - because the insurance has changed. They couldn't even tell me themselves on which insurance I was on their system? Then in beginning of August I made payment and took the proof in to the shop where they made a copy and unblocked the line, more than a month and half later, the statement said that I still haven't made payment. Now how does that make me look on the credit score??I sent MTN an e-mail and asked that I wanted a settlement amount, I DO NOT WANT TO BE WITH MTN. I can't see why I have to pay the rest of the instalments as I am going to lose the monthly airtime anyways.