MTN BAD SERVICE NOT ABLE TO RESOLVE MY COMPLAINT

was due for upgrade in nov 2015, only upgraded end of jan 2016 to a R670 contract pm, only to find when my d/o went off I was charged almost R1000, when I phoned the call centre I was told by an agent, I must still pay my previous contract up which is now included in my debit order, I disagreed with him as it didnt make sense to me cause when you are eligable for an upgrade the previous contract stops and the new upgraded one kicks in, then I was told \he didnt force me to upgrade\"?<br> I logged a call at the store I upgraded in beggining of feb, phoned the call centre today to follow up and where told I wad charged more cause I need to pay off the previous service provider which was nashua? I also told him I dont agree, as my contract was taken over by mtn when nashua closed down. He said my old contract expired feb, so I asked him what my next debit order is, he then said nine hundred and something, I then told him this is my problem : why am i charged R900 if I signed for a contract of R670 and my old contract expired feb???<br> I need this resolved!!! The mtn agents are pathetic and treat s person with no respect! They cant resolve queries"