I found out yesterday I have to attend a conference at the Capitol Hilton, Washington DC in mid-June. There was a conference rate that is no longer available, but yesterday there were still several room options available online for my dates. I had to wait until today to reserve because I was waiting for the flight arrangements to be confirmed and didn't know if I would need two or three nights.

Unfortunately, this morning (only about 12 hours later) when attempting to make the 2-night reservation, there are no rooms available at any rate. I telephoned the hotel directly to ask about getting a room under the Diamond reservation guarantee (I'm still 3 weeks out), and she advised that this was impossible due to the level of bookings.

I have a hard time believing that they are so oversold between yesterday and today that they aren't willing to invoke the Diamond guarantee for one room. I don't really want to find another hotel as I'm not familiar with the area and it's going to be a full agenda with an intense two days of meetings plus in-house dinner, and would be really nice to be able to pop to my room for a 10-minute breather between sessions.

What is the best option for trying to push the Diamond guarantee - the hotel directly, the Diamond member phone number, Diamond email address, other? The representative I spoke to said that if I phoned again, to ask for 'in-house' or 'group sales' although she herself claimed to be with reservations for the specific property (not a central reservation line), and I'm not trying to push the conference rate since I've technically missed the deadline for this, but just get a room at any rate at this point.

If I am able to get a room, I also have a colleague in the same situation. If they were able to book 2 rooms under the Diamond guarantee, are there any drawbacks to doing this for my colleague? He would need to pay for his own room and I wouldn't be trying to get Diamond benefits for him; I would only be trying to get him a room in the same hotel as a favour.

Thanks for any advice.

Susan