What we are using, when a call is answered, an url will open for creating a new ticket. in the create new ticket modal, i can either search for exiting contact or create a new contact in the modal.
If exiting contact shows, then it will show me all his ticket, for which i can click and open if the call is about an exiting ticket, or if i need to open a new ticket, i have that option too.
but having the phone number recognize in the db, and follow your propose action, makes more sense i suppose 😃