Sometimes IHG sells "Best Flexible Rate" as non-refundable, pre-paid. Maybe that's what happened to you? I've almost run into this issue a couple of times and I blame IHG for that.
Since you've already talked to everyone and no-one is willing to help you, the only possibilities left are:
- start a social media shitstorm
- start a class action law suit
- manage to live without the $900 until Christmas
HTB.