Dishonest sales consultant

I took up a one year contract with MTN last year November and this year August I received a call from a lady called Nosi who told me that she works for MTN and would like To let me know that I am due for an upgrade, I took the upgrade offer however she never disclosed the fees I’ll be charged with. I remember asking her that I just received new data for the month the day before she called me and she said it is not a problem as they will erase that data and load the new one. I even asked her how will they be charging me she confirmed that it’s going to be the new deal amount with is R299. To my surprise I received my invoice yesterday and the amount due is ridiculously high. I called MTN and they informed that due to the fact that I took and early upgrade they now charging me extra because of that. NO ONE told me about going to be charged more money for taking an early upgrade because I was not going to agree, I was going to wait until end of November. Mtn is now transferring me to Summber Mobile however no assistance is being provided. I want this upgrade to be cancelled please