Unless you have an employment contract or a union agreement providing otherwise, you can be terminated, suspended, reduced in hours, or changed in your work conditions and terms for any reason at all except an unlawful reason. A report by a manager of conduct that you contend you did not do is not an unlawful reason for employment action.
I know you think that you have witnesses that can testify that you never did some alleged action. But the fact is, you don't have such evidence. That kind of evidence is not possible. You may have wits to testify that at a specific place and time certain alleged actions did not occur. But that is not the same as evidence that some alleged conduct "never" occurred. It is not possible to prove that some described conduct "never" occurred. No wit can be a credible witness to all of your actions and conduct.
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If the person you are calling your "boss" at the place where the security company you work for posted you is the one filing grievances against you, then it is obvious that the security company re-assigned you probably to make the client happy, regardless of whether the complaints were correct or not. There was no wrongful termination since you still work for the security company; only your job assignment has changed, along with a resultant salary adjustment. Unless you can prove the action taken against you was for impermissible discriminatory reasons, which your posting does not establish, then you have no discrimination claim.