I WANT MY MONEY BACK!!!!!

I swiped my bank card at Rich Durban, before I had swiped my card, i had checked beforehand on my Standard bank app if I had enough money to make the transaction and I did. The transaction only went through days later when I had no money and I have been charged an extra R100. I do not have any money to pay that R100, it is not my fault that the transaction went through days later when I had swiped at that particular time, I am a student with no income and no Nsfas, I do not have money so I am unable to pay the R100 is errors right now in my account. I used the app like we have been told to do and made a conscious transaction, I am not at fault here and I would like a full refund for my R100