It sounds like you're wanting to change which Apple ID you're using for your iPhone. I want to help you make sure you're using the right Apple ID.
If you want to change the Apple ID used for the iTunes Store, iCloud, App Store, and Apple Music you will want to sign out of your current account and use a different.
Please be advised, all purchases and downloads from the App Store or iTunes Store will no longer be accessible once you've changed accounts.
If you are not accidentally on the wrong Apple ID, you do not want to sign out and sign in to a different one.