MTN debiting me for a cancelled contract

I received a phone call from MTN around June telling me my laptop contract was about to expire, I then called them and cancelled it and took a data deal only. When I received my bill I saw I was still being charged the same amount so I called to find out what happened, the lady I spoke to told me I had not cancelled my contract it was still active. She then transferred me to customer retention where I was waiting for over an hour until I dropped the call, I called again today ref number: ********** 91 now I was told I upgraded my contract & the guy said he can't help me & put me through customer retention yet again and I have been holding for over 30mins now. Is this a way they try to ***** our money? The staff is the most *********** in the whole world. It's like they do not provide training for them, for how long must we tolerate this incompetency? We deserve value for our money