Over debited

I have a contract with cartrack for 2 vehicles which is R99 a month each for 2 vehicles my premium is R198 month in the month of December I was debited R758 when I called in and spoke to a consultant he could not give me a reason has to why I was debited R758 and all he said was my contract is R99 a month per vehicle. I have requested him to send me invoices as I do not receive them and he advised that a ticket has been logged to query why I was over debited. After a few days of me not getting any feedback I called again and was assisted by a female who was very rude and refused to give me any feedback with regards to a refund or why I was over debited and all she said was I need to wait for a call from cartrack. Its been over 3 weeks and to date I still do not have any feedback regarding the amount I was debited. This is very unprofessional