Charging clinets a penalty fee for paying their account early.

First time ever that i hear a client has to be charged penalty fees for paying their account early. I phoned customer care to find out why i receive an SMS to state my account is behind only to be told that i may not pay my account early and should i wish to do it i have to pay 5 days before the debit order is scheduled to go off. This is something that was not once disclosed to me and only since last month i have seen that vodacom has tried to debit my account, prior to that i have been paying via shoprite or via the app and not once has an agent from Vodacom contacted me to inform me that it is a problem, they just sit idle by and charge me a penalty fee for paying early.