Create a new version of the app by following these steps:
Getting a New App Version
Once the new version is setup in App Store Connect, you will be able to change the name in the App Information section.
You also need to change your app name in the Edit section of MagCast (Setup menu).
Ensure that the App name you use is identical in MagCast and App Store Connect.
Once done, you can submit your new app version to Apple for Review.