Bad service

Hi, I have a very bad experience with MTN, I even regret being their customer. I have a contract with MTN from last year until I realized they have not being debiting my account and there is no excuse as they debit the 1st of every month. I went to their store couldnt find help. I also called them while no one has called me to tell me my account is at default and I am in arrears. I stayed for more than an hour on a call with no answers. The consultant told me their system has issues in the past months and alot of people are affected my the billing. This morning I get a call from the from a debt collector saying I am being handed over, how am i handed over when I spoke to someone and I am awaiting feedback on what is next. I sent them an email no respond. MTN is the worst service provider.