Incorrect deduction but I must wait for money

Last month on 14/01 discovery debited my account for no reason for R514. I contacted them. They admitted it was their fault and would refund me. I only eventually got the money back on 22/01. This was because they supposedly had to wait for the money to appear in their account. They told me it would not happen again. Well surprise again this month I have been debited an extra R500. I am being told they found a problem where they debited some clients incorrectly and are doing the refunds but again only when the money appears in their account. So Discovery make a mistake and ***** my money and now tell me I must wait to get it back. What kind of service is that. They made the mistake, they must fix it. If they want proof of the deduction on my bank statement I am happy to provide that but I expect the refund to be done today!