undercharged a customer

Location: Texas

i am a service cashier for a dealership and it was my first week doing it. i accidentally charged a customer the PAYABLE instead of the DEDUCTIBLE on an extended warranty ticket. i was told the next day i messed up so we called, he said he’d come in to pay the missing $500, but never did. is this going to come out of my check or is he responsible for not paying after being notified. it happened around two weeks ago and i stress about it daily. thank you!