Ok this actually happens to my friend not so long ago, he is going on a boxing match and he will bet for the heavy favorite, then suddenly an unknown guy whisper to him, that the fight is going to be fixed and he supposedly heard it from the favorite to win, locker room, are you going to listen to that and bet for the underdog.
What's your take?
My action will depend on who this person who tells that is.
If he is a reliable or I know that he knows then I would change my bet. At least, I would place 2 bets for both results and make profit in both ways without any real stress.
If you are just an ordinary person, you would not know if the fight is fix or not, especially if its a popular fight where there's big money at stake.
Just don't take it seriously and go with your guts, that's what we do as a gambler and we need to be clever all the time.
When analyzing the fight, always consider a possibility that the game could be fix and what I learned is I don't bet on the heavy favorites as when most money are in that favorite, there's a chance an upset will happen.