Bad service from vodacom

Please could someone assist me, i am so fed up with Vodacom and their poor service and useless call centre agents😡😡😡😡 i took out a data contract in May 2024 and my billing date was the 1st of every month wich was fine. Just before the end of November i calles in to change my debit order date to the 15 th of each month, the lady wich i have spoken to never told me there was a missed invoice amount that vodacom never billed on my account. On the 10 th of december i recieved a extra invoice amount then my account was double the amount. I called the call centre and the lady said vodacom did not bill my account because they dit a audit so i have to pay it even though she said it is vodacom’s fault and i said to her my itc wil now be affected and she promised me no it wont its just a extra amount. I said ok double deduct on the 15 th but the debit order went thru yesterday the 17th of December because of the public holiday. I just went on to experian and transunion and there it is a missed payment on my credit profile and shows now i am in arrears and my credit score went down by 14 points😡😡😡😡😡 now i phone in the call centre and they cant assist me please help this is really so unfair towards a customer