this is why people like you get taken advantage of a lot. They know you won't fight back and even if you do, you back down immediately thinking you can go back to the status quo.

I got sent to voicemail so I just let them know that I applied for the promotion, and then yesterday got denied it for what I felt were pretty dubious reasons, and that I was just trying to keep him updated on what was going on from my end. I don't want to sound like I'm trying to make an issue because really I'm not I'm just trying to protect myself and my job. "

What you should say when you call back is that it feels like retaliation. Don't try to justify it or help them, they did something illegal. Stop letting them walk all over you. They are going to treat more people like this if you let them get away with it.

I'm trying to make an issue because really I'm not I'm just trying to protect myself and my job.

that's never going to happen. Your job is gone. They're going to find a reason to fire you ASAP and try to get you away from them so you won't sue. This is specifically why corporate told you to call them, they want to minimize liability and the odds of a lawsuit. Stop defending them, stop minimizing stuff, and stop trying to keep disarming the situation. They fucked you and tried to steal your money and were about to fire you. Why are you trying to help them?