Hidden phone in Telegram account privacy settings

You will not be able to write to the phone number of the user who hid it in the Telegram settings (Privacy and Security). This does not happen often, but it happens, then it will be possible to write only in @username.

By default, all accounts have - My Contacts, and you can write to this user from the ChatApp integration.

If the user chooses - Nobody-MyContacts, then from integration he can only write to @username.