A:
Sounds like your installer didn't get the bracket bolted into the wall level.
1st I would check to make sure the brackets bolted to the TV are even with each other.
If the wall mounted bracket is noticeably out of level then the only right way to do this is to remove it from the wall, change the mounting position to where you'll get a good anchor with studs, mark hole locations, level and square and drill, and mount.
You should only need to move the wall bracket up or down from its current position only about 2 inches. You can always adjust the brackets on the TV to adjust for the change in position of the wall bracket.