mtn has got a very poor service

I am not happy about mtn service. I have a contract for a rooter 50 gb anytime for 205 of which it has expired last year December, then I got a call after that from mtn asking me to upgrade. The lady who was calling said if I do not upgrade then they will continue debiting the same amount and I'll get same data then I did not upgrade because I was satisfied with that 50 gb anytime. Gues what immediately after dropping a call there was a bank notification of 1200 some cents debit order agreement from mtn of whith I knew nothing about it then I did not accept. On the 12th that month mtn gave me 40 GB instead of 50 and that 40 it's 20 day and 20 night while I was receiving 50 anytime. I called mtn they said I must email them, I wrote them email then they did not respond. I went to mtn shop they said they are not able to help I must call mtn and if I cancel they will charge me because I did an upgrade. The problem is that I did not upgrade to anyone, I never did an upgrade and I was helpless then I decided to dispute their debit order to draw their attention but still they don't call me instead they triple debit on my pay day while they closed the simcard since from last month. Mtn ****med me 💔