After upgrade mtn blocks my sim for no reason

On the 2/8/15 renewed my contract and received the iphone6. It took me some time to download apps and settings. I then noticed that i have not received any calls? On trying to use my phone noticed that it does not work. Made a total of seven calls to mtn with no luck! They said all is fine from there side. Took the phone to greenstone where i renewed contract and after more than an hour of waiting and checking the phone they fitted another sim and it worked. We did a sim swop and was told it would take about 2hours to be activated. Sad to say the same problem happened. Phoning mtn again and after long discussions the found that my sim was blocked for no apparent reason. I was then told it would take 7 days to lodge the query?? This is un acceptable and if it is not sorted within 24 hours i will cancel contract as mtn has not for filled there side of contract. Cell C is prepared to buy out the contract!!! In the meantime i cant even revert to my old phone as my sim is blocked?