no decent answer no solution to my problem

I got a contract with mtn just about less than a year ,initially it was R50 a month ,so I used the sim maybe a month or two then mtn started charging more when I seen that ,,I heard it was a recycled sim ,another man's bank details were coming to my phone ,I reported that ,the man had some subscriptions that were now charged to me ,,they gave me a new sim after I said do something or I won't pay ,,prior to that I had to change my phone as that too had a problem so my installment went up ,,I didn't know so I could have missed a month but other than that since my sim was changed I never got to use it again ,I have been emailing them back and forth,going to branches ,everyone gives me a new story ,each month I pay using the same account no and details yet they say ,its always a month or two they can't pick up ,my payments and I've emailed proof...What must I do ,,I'm paying for something i can't use ,,that's more than a breach of contract ,I tried phoning them on 808 a little while back still after 1hr 20 mins later just a silly song repeated and no assistance ,,so when does it end and when can I get a decent answer and real help please because that's all I ask ,,what is wrong ,show m