I got put in a 40-hour work week on a 28-hour limit

I am currently a 内定者 for a certain company. My Visa however puts me in a 28-hour weekly limit. As the title suggests, my employer has put me in multiple 40-hour work weeks next month. I know they are fully aware of my 28-hour limit, because they made it a point to make it seem that’s a problem when I first started. Two of my coworkers have went back to their home country, so I know management is in a tough spot covering shifts for them as of now. However, it was not communicated to me beforehand that they were going to do this.

Is this normal? Should I say something? Has anyone else experienced a similar situation? Thank you in advance