I've done the phone in pre-check in at the GCH a couple of times. I don't have the number handy, but I am pretty sure it is just the hotel's main line front desk phone. You can call a couple of hours before you arrive and say you are on your way, when you expect to arrive, and then they will get much of the processing done with you on the phone. It saves time when you actually show up (you still have to go to the front desk) but once there the processing is lickty split b/c much of it was already done on the phone. They assign you your room at the time of the call (though they don't tell you which one it is exactly until you arrive at the front desk.)