Shower niche tile unfinished edge?
That is not a professional job. Good thing you have not paid in full. That needs to be removed and redone properly with bull nose and polish the edges of the glass tile so they meet properly and not show such a wide grout joint to cover the edge of the rough cut glass tile. This is something THEY need to do. What I suggest is common practice that is done by professional tile setters. I hope they can do you justice.