Delayed payment

I am so disappointed and disgusted by FNB, a purchase that I made on 26 March 2021 only went off my account on 16 April 2021. I literally used my last R500 on that day for petrol and groceries for the rest of the month. Now my account is in overdraft with those payments still pending. Had I known there was a delay with that payment for 26 March, I wouldn't have used the R500 and now FNB cannot help me in anyway besides giving me a loan. It's such bad service from FNB, I had more than enough funds at the time of purchase and now they want to put me in further debt because of their mistake.