Poor management a

I'm so disappointed at clicks carnival mall I was there on the 23th july I tried to purchase there I have medically with R80 and the transaction for my purchase was R174 so I wanted to use my medically account to pay the difference but it seems like the cashier didn't know how to do it.it keeps on declining and I ask the cashier to call the manager to help as it was not the first time it happens and last time he help.but today when the call him he just said there's nothing I can do.he didn't even bother to try and check it and I keep on showing him my massage on my phone the amount I have he just sad there's nothing I can do.im slsk a manager were I'm working I would never said that