Card Machine Purchase has to be R10 and over

I just went to your garage in Sherwood to buy bread.17/06/2024 @ 13:30 and I had R21 in coins to make to make the purchase however the loaf of bread was R22,99 so I was going to pay the difference via my bank card and they declined me from making that purchase because they said I would have to make a purchase over R10 on their card machine.Which is ridiculous because I work for a bank and you can purchase any amount even if it is R1, Cash is cash. I even wanted to talk to the manager that was on duty however but he told the cashier to tell me that it’s their policy. There is no policy even on the door to state that. What ridiculous service I received and will tell everyone I know not to fill up there