certegy check service I went to Pet Smart to pick up my dog when we returned from vacation. I tried to pay the bill with my credit union check. But Certegy denied the transaction.Even though I had done so in the past. I called certegy to find out why and got a big runaround. At first I could not get any information other than the computer had denied the check. Great - computer again- as I pressed for a answer I was finalley told that the check number had been used before. This was a lie. I checked with the credit union and ascertined that check number had never cleared or had been input to their system/ Certegy denied my check for no reason other that the COMPUTER did it. and the lady could not tell me anything about it. This company is a rip off do not use any firm what uses Certegy for check verication because they don't verify anything. Ontario California