Brian,
That line has been busy for two days so they either have a phone problem or it's off the hook. I made several calls this morning (India I think)
to try to increase or room block but their group sales office is closed for the Holiday so I won't get an answer until Monday or Tuesday. If I were you I would book at the Comfort Inn or Holiday Inn to make sure you have a place to stay and if we can arrange for more rooms at the Hampton you can always change your reservation if you choose.