MTN Billing woes

I have tried since 27 May to resolve a billing issue with MTN. They suspended my PAID account after their own error with double debiting. The social media team is really not helping and I'm at my wits end. No one even bothers to call to resolve my issue and just this week I received an invoice with a cancellation fee that I must pay in 14 days. In all the 15 years or so that I've had this account, i never missed a payment. And at np point did I receive a cancellation. I remain without service. MTN has the WORST service in SA.