Corporation promised promotion with raise and bonus benefits. Employee took over the position and has fully taken on the new responsibilities but has been continuously blown off by management when asked when they will sign paperwork and receive official pay increase/position.

I have no idea what to do in this situation. It’s been well over a month working my “new management position” (took it over after my previous manager left). I’m afraid to threaten legal action because I’m at will and can be fired for any reason. I don’t want to stop working hard because I am afraid they will fire me or take back the offer. The corporation is too large to even get a hold of HR or anyone who can answer my questions. Don’t want to lose out on this opportunity but I feel taken advantage of and am considering quitting. Any advice?