tma you shouldn't need to install that app on your owner.
Open the built-in Graphene Phone app in the owner.
Go into the settings (3 dot menu in the top right). Hit Settings.
Go to Calls - > Calling Accounts.
Make sure the Calling Account you want appears there. If it's an esim, make sure you toggled on esim support in the owners settings -> network & internet -> esim support. This will require a reboot.
If this isn't what you're asking about, could you try rephrasing what you're asking? We might be thinking about different things.