Bad Service

I am very disappointed at the service Telkom gave me. I was due for an upgrade on my contract. I have 2 lines which are with Telkom, and I have been using their service for over 3 years now. There were two debit orders that got rejected by the bank but I paid cash, which was for me the other alternative method of making payments. To my surprise I was told that my upgrade could not be approved because I am struggling to make payments. I have been paying religiously for the past 3 years and haven't skipped payments. The only thing was the method of payment used. Why does Telkom treat customers like they are owing them something.