How to delete unwanted underlining on spreadsheet

I am using a MacBook Pro and have two spreadsheets with underlining that I have not created and am unable to delete.

Command U doesn’t work.

How can I solve this problem?

Thanks for your help.

Perhaps Menu/Tools/Automatic Spell Checking

What type (what line type) of underlines do you mean? Can you upload an ODF type sample file here?

Perhaps hyperlinks?

Or a cell style?