MTN DATA Contract

I signed for 2 years MTN Data contract on 2017, then when that contract supposed to end they called me to continue with another 2 years contract as they run promotion so they give me that promotion for 2 years. So when that contract come to an end they didn't remind me, they deduct x3 of the actual price, then i called them they said don't worry it's not your fault, they confirmed that it's their fault not to cancel the contract, i said Ok, then i reverse that money as i made an agreement that they have to deduct the correct amount end off. End of that months they go ahead and deduct more than that, i decided to cancel the contract, i called them they said they will call me within 24hr, that 24hr passed i called them they said 72hr that 72hr passed. Tell cancel my debit order and said i must go to store to pay by cash, I went to store and pay the money that i was owing them, as i can't pay for their fault issues. They didn't want to cancel my contract up until today. The money keeps going up. When i call them said i was suppose to call MTN contract department then i ask them, on which number they said 135 then they'll transfer me, i said please give me the reference that i got the time i log to cancel the contract they ask me what am i going to do with reference? Till today they refuse to give me.