Taking charges without warning.

Bank charges didn't come off like they usually do on the 10th just my normal cheque account. come to the 21st paying for petrol and my card is declined why because I have R130 left in my account!!!! why cause fnb decided they want to deduct the money now a week before payday, now I can except that the charges should come off but warn ppl, heads up something. I could have said take it the 27th to play it safe but come on R130 rand left in my account and I look like an idiot paying for petrol when I have no money to pay for it.