Stick with it. If you don't get a satisfactory response in a few more days, try a trick I've used with great results.
Bypass "management" and look up the EXECUTIVE leadership of the company. Send a professional letter of complaint to each - starting at the very top. Make sure to "cc" each recipient so that each one knows who else is getting a copy. It's been my experience that they'll each scramble to resolve the problem before their boss calls them on it.
If that doesn't work - please name them.
Hotels have a great deal of latitude to grant free rooms on non-peak nights. I'd expect at least a couple of free stays as compensation.
You say a reply came from the U.S. They could get quite a earful from those of us offended by their treatment of one of our own.
