Originally Posted by
blase
I emailed Cust Service on 8/27 to remedy this, and still have not received a response, other than their auto generated email stating that they will respond to emails in the order in which they were received.

You emailed on the Thursday before a holiday weekend, also the biggest vacation week of the year. I wouldn't expect an immediate email response.
If you want an immediate response, pick up the phone. Call the 800 number or the LAS location directly. I would do the latter, asking for a double credit to bring the balance to zero.
If you call the 800 number you could ask for the same or for a credit of the overcharges and a voucher to a future rental (could be $50, may be worth it).
I doubt the overcharge was done intentionally. They have bad systems which default to the fuel service charge unless overridden. An employee under pressure will easily make a mistake, and you weren't there to catch it.