I rented a car from Hertz at the Willow Run airport, YIP. This was my only time flying on a private plane and dealing with a FBO. The car was delivered and waiting at the plane, awesome!

​​​​​​I returned the car to the same location. I parked outside the FBO, gave the keys to the receptionist who told me I was all set. The bill was supposed to be around $200. I honestly didn't think about it again.

A couple of months later, I was charged approximately $1600 on my Amex, and received a bill from Hertz purporting to show the car return many days after I did.

I called Hertz and they said they would investigate but not inform me of the results. I disputed the charge with amex who credited me the difference within a day. Now, three weeks later, my Amex has the disputed charges back on my account.

Any suggestions? I have zero experience with FBO's and private airports, and probably won't again.

Help!