If you have set up a Centrepay payment, they will pay the amount when you ask them to.
If it's overdue, you really need to get in touch with AGL or whoever it is first and explain the situation. You may need to pay a small amount to keep them happy. You can always pay in small instalments before the situation gets to this situation, even if it's $10 a fortnight.
And definitely look at a financial counsellor; they won't judge you.