DCA Commission

Have to say I am a bit disappointed given the long standing relationship I have with wesbank, on my second car now financed by them - never had anything to complain about till now when I looked at my account. My installment are paid on the 1st monthly but for the month of December manged to pay on the 18th. Upon realising I'm gonna be late on payment I took the liberty to contact them and informed them that will pay on the 18th which happens. But just realised that there's R462 DCA commission, how did you guys come to such a hefty amount, for what. It's not like was avoiding payment, it's not like letters of demand where sent. Can some contact me to explain how did you guys arrived to the conclusion of charging G me such amount