I have my doubts that I'd get results when calling (at least not without a very long phone call).

Fortunately, this is a physical merchant (hotel) that I'll be passing by (during midday hours) on Monday, so I'll stop in while the manager's there and show them both cards, priintouts from amec.com of the right card being authorized and the wrong card being charged, printouts of the folios with only the last 4 digits showing, and hopefully with all that they can fix it. (Or, at the very least, they can presumably wipe the old card from their system so this doesn't happen again on my upcoming stays there.)