Changing my schedule without communicating with me

I’ve been with the company for about 3½ years, and since I moved to this site almost a year ago, I’ve been working the same schedule: two overnight shifts and two mid shifts.

Today, I received a call from my account manager saying they’d “finally fixed” my schedule, even though I never complained anything about my schedule. I’ve never missed a shift or been late, so the call really caught me off guard.

A few days ago, my coworker had a meeting with the account manager because he missed a few patrols due to a miscommunication while he was working with a sprained ankle and wearing a boot. Now, it looks like they’re changing his schedule as a consequence, possibly trying to get him to quit, while giving me some of his overnight shifts.