UPGRADING OF MY CONTRACT WITHOUT MY CONCERN

I signed a two year contract with MTN in December 2014 with a Samsung Galaxy Tablet 3 the handset had technical problems within six months - battery was dying within 2 hours. When I went back to MTN Stores in Midlands Mall they didn't even look at the handset but they referred me to Save Supermarket where there we SAMSUNG consultants. They said the phone had to be send in for check up and they needed R280 to back up information that I didn't have so I had to leave with my phone.<br> <br> Beginning of December 2015 I called in to request my contract to be changed to prepaid when it expires, to my shock I was told I have upgraded till 2017. I never signed or agreed on any upgrade. A fault was logged and I was requested to phone after a week for an update but when I checked it was still pending. in December R210 was deducted from my bank account and now in January I am sitting with a tax invoice of R500 and some change. finally I got a consultant who was helpful who said I need an affidavit to report the case. I was never told this before. I am so frustrated and devastated with the kindly of service MTN is rendering. I don't know what to do to stop the January debit order