MTN massive overcharging debacle

In regards to a billing fault that shows my account payable is over 5 times what it is supposed to be on the mtn app. Monthly fee set R0 in excess of contract fees at time of signing and again confirmed over the phone during the following process

After contacting the mtn call centre 3 times because of what they refer to as "a change of system error" I was assured it was resolved on all occasions, yet the figured remained. This all occurred weeks prior to the billing date. I assumed I had done my due diligence and that the matter had been resolved. Low and behold today I am debited the far larger amount. In the middle of a situation where I can by no means afford to be debited almost 6 times the usual amount (during the COVID lockdown my income is exactly R0). To top it off they are uncontactable. I'm hoping I have some grounds to terminate the contract but at this stage it's like being ****** by faceless entity as no contact portal seems to be operational.