cashback

Today I got a notification from the bank I used to bank with that the cash back money was transferred to my old account. My issue is that the money was not supposed to be transferred to that account since I no longer use the account and my banking details were updated from your system. Last month I sent an email to GS enquiries and I was advised that money will be transferred to my account in August and I have to submit proof of account or a bank statement. Who gave you guys permission to transfer money to my old account?? I need this to be fixed ASAP because I didn't give permission for money to be transferred to that account and you don't even debit from that account. My details were updated sometime last year, please fix this mess.