Telkom charged me an extra R202 but it's their fault.

Telkom are charging me a debit order rejection fee of R202 after they tried to debit my account before their normal debit date. They did this on Saturday 30th of March, not on the 31st. I then received an sms on the 1st of April telling me to pay the amount before incurring charges, and I did immediately. However, today(May 9) they sent me this month's invoice and it includes an extra charge of R202. I don't understand why this was not mentioned throughout April.