Merge and Center Gridlines

Hello all, I am creating a spreadsheet for Fantasy Football. I am trying to keep it pretty simple, but I have run into an issue. I have been using merge and center on vertical cells, which I have rarely done in the past. It worked fine on all but one part of my spreadsheet. On a certain portion, I click merge and center and the text moves to the center of the two cells, I can click on any are and the whole cell will be selected, however the old gridline from when they were two cells does not go away. I have tried changing all kinds of border settings and things, but cannot find a way to fix this. This is only happening in one portion of the spreadsheet. Any help? Thanks!

Spreadsheet.png

Alright, I found that if I unfreeze all the cells, the lines disappear. I would like to keep the first four columns frozen. Anybody have an idea how I can freeze those four columns and get rid of those lines?