Closing in a window opening on a cinderblock wall
You have several issues: 1) proper mortar installation, 2) mortar on face of bricks, 3) contractor’s license.  

1) Laying bricks is not just sticking mortar between the bricks. Bricks are embedded into mortar. The bricks should be clean and wetted prior to COVERING the bricks...it’s not acceptable to jam a little mortar between the bricks because it will not bond, will not be watertight and will be susceptible to spalling due to frost, moisture, etc. 

2) Mortar must be removed immediately from brick faces or it will stain the face. The only way mortar, that has aged on the face, can be removed is with acid. Using acid will remove the finish and cause the brick to leak (water penetrate into the brick). Then, a strong wind will drive rain into the bricks causing damage from moisture, mold, etc. Also, frost will crack the bricks. 

3) I would check with your local Builders Board and see if they are licensed contractors. I doubt it. You can see if they have claims against them and you can file a claim against them. The builders board will investigate and make a determination. I’d call your local Building Code Office.