got called a liability because they aren't scheduling within my availability

I started back at my old job from last year with the agreement I would move stores when an overnight spot opened up. well...... as of 2 weeks in, something did open up. I asked about moving into that spot and was told that, "That's not something I can do right now. I don't have anyone to fill your position." Now I could totally understand that, however I was never hired into a position. They didn't even have hours for me. They are using me for filler days and filler shifts that they already had covered.

I would be okay with this if A) my hours were consistent, B) I was given overtime at other stores, or C) I would be able to have an unchanging schedule. I checked my schedule 3 days ago and was given 35 hours for next week, GREAT. I looked at it last night and noticed she had taken one of my days. This is after the conversation about how I would need to move to overnights soon. Not to mention, and again, not trying to be funny, if you can fill that spot, you have people to fill in the hours that I'm currently working.

I did the only reasonable thing I could think of, I reached out to my bosses boss. I told them it was agreed I would move to overnights when something opened and was told that I'm currently a liability because I haven't been feeling great. I said okay and left it at that. The agreement was never for me to work mornings for longer than a few weeks but rather for me to work overnights when something opened and then I would move stores. This was understood from my boss to her boss all the way to her bosses boss. They're now acting like they have no clue what I'm talking about.

This is honestly fucking ridiculous. I told the store I'm trying to move to (I'm cool with that manager) that if I'm really, and I'm not trying to be funny, but if I'm that much of a liability, they should be happy to move me to another store where they don't have to deal with that.