over debited

I took out once off loan from Kempton park branch, and for unknown reasons my account was over debited on the date we agreed for a debit order. and I contacted the branch for a refund but the guy by the name of Raymond told me that there's no way i'll be refunded if i don't show up to get the money in cash from the office. how the hell because when u take out a loan they say they don't provide cash but gives you a debit card? now that they messed up they issue cash