Errr, I'm on the side of the first person you spoke with. You acknowledge it was your fault as you had forgotten to pay, you have accepted the service providers Ts&Cs but think it is worth chancing your arm again and you got lucky.
I wonder if the charges would be lower if your service provider didn't roll over every time they paid out to forgetful customers?
I have a number of debtors that owe monthly payments and I have a fixed penalty amount for overdue accounts. However if someone can sell me a good story or have a good attitude I can quite happily waiver the penalty.