Manipulated into doing overtime

I got called into the office during my shift.

My manager was concerned about what's going on outside of work as I'm not as willing to do overtime as I was during Christmas.

Basically he said that as I have full availability, he can schedule me whenever he wants but doesn't because he "prefers a better relationship with the team even if it takes a hit with the relationship between him and the store owner"

So I said ok I'll do some overtime but then later on in the day I'm like... in my head... I'm contracted to 22.5 hours a week, availability has nothing to do with scheduling me overtime it's just how available I am for contracted hours.