Cashback: Forcing customers to buy something

Visited the Vangate mall spar for my daily shopping. After I had paid (using my Credit Card) I told the cashier I would also like to withdraw/get a cashback (with my Debit card). <br> <br> The cashier then informed me that the system doesn't allow cashback/withdrawals if an item from the store is not part of the transaction. I'm not sure if the cashier was instructed to say this or if the system really doesn't allow it but this is highly inconveniencing and I will not be visiting a Spar ever again. A few months ago I was able to get a cashback without purchasing anything in the same transaction so why has things changed? If this continues, I definitely won't be visiting a Spar in future as I don't have this issue at the other major retailers.