In January 2016 I volunteered to get off a United flight from Denver (to make space for a crew member) and take a flight the next morning. In exchange I got the night in a hotel and a $1000 Electronic Travel Certificate. I've done this a few times before, and have not had any trouble using the ETCs. Yesterday I tried to use this ETC and found it had been canceled after issue by the gate agent in Denver. This is unacceptable--they offered $1000, I accepted the offer, they gave me the ETC, and I expect to be able to use it. I called reservations to see what was up and they said I must contact Customer Care via the website, which I did right away. I convinced reservations to hold my reservation for 24 hours so I could still get the flight and price I wanted, but Customer Care has not responded yet. Does anyone know a number to call, besides reservations? or any other strategy to get this kind of thing straightened out? I am a MP member but not premier or anything special. THANKS!