Arrears that aren't arrears

I can't seem to successfully resolve the matter of FNB claiming that my account is in arrears, when there is a set debit order that is deducted like clock work!! It frustrates me that my accounts, and my financial credibility is affected - while no consultant is able to resolve the mystery?!!! THIS is the WORST service I've ever experienced with them... Very disappointing. I wonder how long it's going to take them to resolve this, and restore my credibility.