FNB Double debits leading to Unpaids

I am never one to berate, or bemoan my woes, but I've been double debited with a debit order ( credit card twice, already debited 10 days ago) that has never been missed, and is not being used. The debit was conveniently done before my other debits, resulting in multiple unpaids which I will ultimately pay for? I will be penalised with maximum rates because I missed the payment? Which I never miss? Wow FNB, I'm just a struggling business man trying to make enough pay to sort out all my bills, then this. Please note, none of my accounts were in arrears, until this awesome surprise. There goes my credit history .Wow