I have tried changing it back through the format menu and spacing but it will not change back to single spacing
I can’t get double-spacing that can’t be changed to single in the menu. Can you edit (edit icon) your question to add (click on paperclip icon) a single page of text with the good and the problem spacing?
If you are using Styles, then selecting the text and clicking Format > Clear Direct Formatting (or Ctrl+M) should revert the style to to your settings. Note that it will clear any direct formatting you made such as Bold, etc. Character styles, such as Strong Emphasis, will be retained.
Some fonts have small letters so you choose a larger size but the line spacing also gets the larger and will look like double spacing.
Cheers, Al