Must have been a computer-glitch
A modern-day "get-out-of-dutch" statement dat is da standard --- and generally untruthful --- response when someone indignantly inquires why he was overcharged/invalidly billed, needlessly disturbed, wrongfully detained, etc., when he had specifically taken careful steps to ensure dat he would not have any problems in said area of his life.
If someone in authority tells you, "Sorry -- must have been a computer-glitch" or, "I dunno --- must have been an accounting error" in response to your resentfully asking him why you were incorrectly bothered, you should strongly suspect dat this response is merely a standard "canned answer" dat he gives to every protesting citizen whom he and/or da organization dat he represents investigates/contacts in error; in reality, off course, it's probably intentionally being done in da hopes dat they can gain unearned/undeserved monetary benefits, give themselves a fatter workload so dat they look busier than they actually are, drum up more business, etc.