Hey there @nostedna,
Welcome to the Community and thanks for your post.
That would all depend on the type of phone that you have.
If you have a smartphone and need to access your text messages while on a call, you would simply need to minimise your calling screen the same way as you would close any other apps on your phone to return on your main screen. Once the phone call screen is minimised, you will have the ability to navigate your other apps simultaneously.
If you're unsure how to do so, check out Phone Guides and User Manuals.
Let us know how it went.
