My Current Job Is Trying To Prevent Me From Moving To A Different Department

I'm in Iowa but both places' main offices are based in Nebraska, I believe. I work for a private company contracted under a bigger company. I'm trying to switch to another department. I do the interviews according to the rules of my job (off the clock, out of the building) and both times I was told I did great in the interviews and all that was needed was to start a background check.

The first time I was not sent any email to start my background check, I waited 2 months, only for info to leak out that my job was strongarming the company into not hiring me because they are losing a lot of people due to us not getting raises, better benefits, etc. I just completed a new interview two days ago, so I'm still in the "it could happen" phase of getting the email. Regardless, what should I do if it happens again? Is what they're doing legal? I really want this job for the amazing benefits and pay.