Billed incorrectly

My payment was due on the 1st of June. I decided to pay via the website before the 1st to avoid an unpaid debit order. Vodacom received the money but they still requested payment on the 1st of June. The debit order was unpaid. Today they tried to deduct for July but they included a late payment penalty for the June unpaid debit order. The funds were not sufficient because I was not aware that there would be a late payment fee. I was not late, I paid in advance. Therefore there should not have been a late payment fee. Now that they did not receive today's payment because they deducted more than they should have, I assume that they will charge me another late payment fee. Vodacom must reverse these late payment fees. I was incorrectly billed.