If your phone automatically underlines random parts of my text Message and you are unable to edit any words in the Underlined area. If you click on the underlined areas, it is highlighted in blue and the copy/past option appears. If you want to disable this see how:
When the word is highlighted, tap hold on the word until the lens glass appear, without letting go off your finger slide left or right to adjust the cursor to where you want to make modification, it's that simple.
Alternatively, you can go to settings> general> keyboard> check spelling/ OFF
You will no longer have your words underlined at the first place. Hope that helps
