Something very fishy

I gave my mom my bank card to use to fill her tank. I transferred R350 from my FNB savings to my cheque account before she left the house. She poured full tank at Engen Dalpark. The full amount was R738.00. She asked to pay R350.00 using my card and the difference using hers, however before the R350.00 transaction went through. There were two declined purchases, I immediately contacted my mom to ask if I should transfer more money and then contacted FNB to find out what they were - and shockingly the petrol attendant had tried to swipe R400.00. When I asked my mom what happened, she said the petrol attendant walked away from my mom with my bank card in hand and helped another customer who was pouring fuel for R400.00 before helping my mom pay the R350.00. The card machine “connected” to my card hence the two declined purchases, apparently this happens often and when it does, the money doesn’t necessarily get deducted, if that was the case why did I get a declined purchase notification and what would happen if I did have that R400.00 in my bank account as opposed to R350.00

This sounds very fishy. My question is: Why walk away from a customer with their card? And if this happens, why not be careful not to let it happen? Declined purchases means bank charges, who’s supposed to pay for those bank charges?

It all sounds convenient, fishy and dishonest to me.

Not okay