Conned by mtn?

On 1st march this year i upgraded my data sim from 1gb to mtn's 2gb package which was on a double your data promotion where you get 4gb anytime data and 4gb after midnight for 89 rands per month. I did this upgrade over the phone and the lady whose name i cannot remember phoned me from a durban phone number. She told me that i would receive a new lte sim via courier which i did receive but a copy of the contract was never sent with the sim. I did not worry much about it as i never had any problems with mtn untill my first debit order went off and i was billed an extra 95 rand for the extra 2gb data. I tried to resolve the matter at mtn carnival mall and the gentleman told me that they have never ran double your data deals and that i need to bring my copy of the contract as proof which i obviously dont have. I feel like i have been conned by mtn. My cellphone contract is now also up for an upgrade and i am not going to upgrade my contract unless this matter has been resolved..........very unhappy.