It sounds like you only have one option if you are so sure they will do that.
Find a new bookmaker.
Weird how in decades of business they have not done this to anyone else though!
You must be a very special person to get so much unfair attention on your betting activity there. When no one else does.
There should be some time limit to act on fixing evidence you think?
I think it's fine to act whenever they have the evidence of fixers trying to steal from the rest of us. Whether the match is over or not.
You sound like you would like match fixers to have a better chance to be paid. Why is that