Poor Billing Service From MTN Affecting Credit Record

I am utterly disappointed with the service of MTN. I have been its customer for over 5years with 3 contracts with them. Over the years they have been deducting the debit 1515th of every month. January on the 15th I received an sms to say my debit order bounced due to insufficient fund and it was on my pay day. Days later my line was suspended which affects all my transactions. I went in store at Mall at Reds MTN, all I received was that they don’t know know what’s wrong but it’s sorted meanwhile I paid in store. I also called the Customer services online 135 the lady advised that there is a problem with FNB and debit orders meanwhile I must pay , I have done so Feb and March.2 and 3 April I received messages to say that MTN hasn’t received my payments . 03 April received a message to say outgoing calls will be suspended. Today 13 April I went to istore I got a shock that I have been handed over to collections department I’m owing R1443.97. 1. I’m really ****ed off as this has negative impact I’m my credit score and record. Unpaid debit orders are also charged. I have been to MTN Centurion mall twice and I was told I need to call Billing. Billing refers me to the MTN Store