Client suffer due to *********** Sales Consultant

Good day I upgraded an existing contract number stating with 073163….. on the 21/08/2024, the end date of the existing contact is in November 2024, the Sales Consultant that assisted me was Nqobile Nxumalo, I specifically asked if the new upgrade can start from November 2024 she ensured me more then once that it will only be payable starting November 2024. In September 2024 I received my invoice that is payable end on September and the old contact instalment (ending November 2024) and the new contract instalment( starting November 2024) must be paid end of September. I phoned in several time with numerous references numbers. Eventually I get to speak with Nqobile Nxumalo, she told me can’t do anything with regards to the mistake made, and now I must make arrangements as if I did not pay my account. The service I received was disgusting, no one wants to take ownership and me the client suffer due to incompetency. I am extremely unhappy