Horrible experience from MTN

I wanted to make an upgrade with MTN and was told that my account has been suspended due to non payment and that I'm 1being behind with two months. I have never ever skipped a payment since 2008. I only asked to change my paydate from the 25th to the last day of the month as a result of changing companies. Now they have changed me to a cash payer and I have been paying via debit order for all those years. It's not even month end but I'm suspended from upgrading two of my lines which are due for upgrades. This has been the worst service experience ever since with being MTN. I have made over 10 calls, some longer than 1 hour trying to get the issue sorted but each time I get nothing but a horrible service!