UPGRADED PLAN WITHOUT CONSENT!!!!!!

They don't even deserve the 1 star that I'm giving them because of their poor service. 29th January I received a call from MTN just after confirming my name with the consultant call got disconnected. Few minutes later I received a email notifying me that my plan has been upgraded. There was no discussion between me and that consultant for any upgrade on my contract. I have continuously declined upgrade because I cannot afford. I have tried to get this issue with MTN same day and I have followed up still nothing has been sorted. My bill is a R1000 more than what I normally pay and I cannot afford to pay it. This will now have a negative impact on my credit score. PLEASE SORT THIS OUT!!!!!!