The top grout line in the shower wall tile is about 2 inches. How can it be fixed?
Don't pay them until they come back and do it right, but since you're asking I'm guessing you've paid already.

To fix, you'd need to get a wet saw or tile cutter and some of the tiles used in the project. Scrape out the grout, cut tile to 2" minus width of your grout lines minus 1/8" to 1/4". Put the tile up with mortar, grout, and caulk along the top where it meets the ceiling.