I don't understand this bit.
If an incorrect charge has been billed to your Amex, tell Amex to dispute it. Don't bother mentioning the stuff about pre-authorisations. You booked two rooms and you were charged three times, the hotel won't help, so Amex should dispute one of the charges.
In response to the thread title, I've never been overcharged at a Hilton when paying using an Amex.
The point is the charge for the second room they are claiming that they did not receive it when and it only shows as a "released" pre-authorisation.
Yet on my side it shows a fully billed statemented/posted charge whatever you want to call it.
So because they claim to have not got the money for the second room they have billed me again on checkout for the second room.
This is in spite of it being a non refundable pay in advance rate ?????
And yes I have disputed it with AMEX - it was done within 15 minutes of seeing the 3rd charge. Apparently it will take till November to resolve ?
The point of confusion is it was a prepay in advance non refundable rate - the money was taken but Hilton claims they didn't get it so billed me again so they and AMEX are trying to figure out what the heck is going on as they are not on the same page right now.