I know this may sound a bit crazy but use your thumbs each side of the bezel applying as much pressure with them as you can while trying to turn it, then turn it 180 degrees and try again, and then 180 degrees and try again. If that doesnt work the only other thing I can think of is trying to use some from of clamp on it but with some soft chamois leather between the jaws and the bezel, it will be tricky trying to get a hold but once it starts to move you should be ok. Are there any slight dents around the bezel that would indicate it has been dropped? even a small dent to the outside of the threaded area would act like a locking mechanism 
Good luck
