Incorrect billing

I am in so much disbelief 😯😯 the service I keep getting from Vodacom is shocking!! I changed my debit order date to the last day of the month as I've been advised by the company's agents. The reason for the change is so that when I pay my account on a 25th the account will be cleared for the month and company will not have to send a debit order request once they can see that the account is paid. I paid my account as suggested on 25th but got an SMS today stating that my account remains unpaid for the month. I am shocked 😳 what kind of a service is this!!!