MTN bad service

Mtn has been debiting after my contact ended with them . they decreased my data to 5g without any communication from 20 gigs to 5gigs , , I've been paying MTN never missed a payment, I've sent 10 emails to Customer service and no answer . Four months before my data contact ended they kept calling me about the upgrade deals and I declined the offer because heir services suck and the network connectivity is super bad . I've spoken to more than 10 different consultants and nothing was done . My statement for February after my contract ended, they charged me R1031 ..I'm enough with this company