Not so useful Key Account Manager

For a few months now, I have been receiving an invoice with amounts different from my vouchers. I contacted Sibusiso Mtombeni (on the 11th of November), who is supposed to be my Key Account Manager, and I have yet to receive feedback on the email I sent. I book a car every week (corporate booking) and every week it is the same issue.

Kindly sort this out as I don’t want to owe you money unnecessarily when my company refuses to pay rates outside the corporate one which seems to be the case - instead of corporate rates on my voucher.