Bank Charges on early Debit Order

I took out a loan with Capitec and they advised that they will debit my account on pay day, but pay day was on a public holiday for April so they debited earlier and there were no funds In the account, they then debited my account the day after the public holiday and the debit order was successful, my issue now is that I was charged R150 for the failed debit order which is not my fault as the contract states that my account will be debited after the public holiday, they are now refusing to refund me the R150 I got charged which is unfair for me, the lady I communicated with is Nomvuyo Ncayo.