Hi,
I know how frustrating it can be to have everyone want to know what your film is about without reading your script but sadly that's what the logline needs to do. Really it just needs to spell out that there's a person, something happens to them and they have to go on a journey to 'solve' the situation (and in doing say undergo some sort of transformation).
Without knowing what your film is about I can only make a condensed logline up:
"After a young boy starts to lose his belief in Santa Clause, a talking teddy bear takes him on an adventure to rediscover the magic of Christmas before it's too late"
Granted what I've written is fairly terrible but gives you an idea of the formula. You should really throw in the obstacle/antagonist but I'm not sure who that is in your story. Maybe his step mom is an evil witch who wants to destroy Christmas...
Good luck