Account tripled after Nashua to MTN merge

This is my 2nd week I have been struggling with MTN,when trying to call them its a disaster. I made about 20 calls and E-Mails to MTN,1 of the ref given to me was ***.The worst thing is that they don't even bother responding. Out of the 20 times I called MTN,i only managed to get through only once.I had account with Nashua Mobile, and last year October I upgraded to a cheaper package.My previous Contract was Anytime 200,and there was a call limit set to it, and the New Contract is My Choice R50,to my big surprise MTN is still charging me with the Previous Contract,and to make matters worse,they removed the call limit,and now my Account have tripled to what it used to be when I was with Nashua Mobile.I have send copies of my Contract to MTN,but to this day ,there is still no response from them. I HATE MTN WITH A PASSION.