I am not aware of such a way. As if you add the user's email address, they will be notified.

Perhaps you can explore the ticket feature of intercom, or if you are using a calls app that is integrated with intercom and they have a different route for it.

@user1911​  Thank you for your answer. The only workaround we can think of would be to use a dummy account with an internal mail address, like receivedbyphone@company.de...