How do I fire a property manager who is unreponsive?

[Victoria Z.]

Hi all, I need to fire the current property manager, I was not able to get in touch with him as he never picks up the phone. How do I do it so I can 1) get him to release the rent for this month  2) have the tenant pay me directly starting next month and 3)have the manager transfer over the deposit and the keys?  How do I do this if he never picks up the call? is there something I can do? I suppose to can threaten with a bad online review, but is there something else I can do? I feel like I am kind of held hostage.