Company put me on PIP without any proof

Hi My company put me on PIP(Performance Improvement Plan) without any proof on May 7,2019. To save my job I had to sign on PIP document. Before that On April 24,2019, I mail to my program manager not to continue with the current project and complaint about my reporting manager and project manager for this project. I cearly said that I won't work with these people. As a result of this, they put me on PIP and took no action on complaints. Instead, they said my attitude and behavior is bad with reporting manager and project manager and they gave wrong feedback. Company has 3 months notice period in the agreement. I asked HR if PIP is failed what will be the exit process. Upon asking multiple times in the email, she didn't reply to my question. Actually company don't need me now. So they want to FIRE me without providing 3 month notice period salary and that's the reason they put me on PIP so that they will escape to give any performance bonus and notice period salary. Please suggest what should I do in this matter.