Disgusting MTN service

I changed my contract in February 2020 asked the consultant who was assisting me if I chabge how will this effect my debit order the consultant said not once you change your debit amout changes to the contract as it has always been for years. That month I was billed for the previous contract on top of it I did not receive the previous amount contractual agreement. I sent an email telling them one 9r 2 consult say no my amount is reduced 3 month they still debit saying I owe them for February my question is how do I owe when I upgraded but did not receive the monthly amount I would have paid for. mtn has useless consultants who dont really know what their doing their managers or whoever is sleeping on the job cause aslong as they make money they are making us customers miserable. Secondly the laptop I upgraded to their vouchers doesn't work they stores cant really assist you menlyn stores cause they jut dont know how and also lazy walking around like they are actually doing something when they are not. They didn't even rica my sim card which I complained still no response and the voucher still haven't received a replacement even today. MTN is useless network no wonder people are leaving it its really disgusting service from all of them.