Demand for answers from Mix Telamatics

I have an unresolved issue on my account billing for July 2022. I noticed from my invoice that the payment for July is doubled. I called the call Centre number on the 02nd and spoke to Caroline who promised to call me back but never did. According to Caroline my contract for the old unit was not cancelled after a new unit was installed in June. On the 07th i called again and spoke to Neo who also promised to look at the matter and come back to me but he also never called. I send a mail and receive a case number, but no any other feedback and I received an auto mail indicating that the case is closed. Can I please get an explanation on how the case is resolved because I don't have the outcome. My budget is very tight so i will not afford to pay double of what i have been paying. I am failing to get answers from the service provider.