Your number may display as Unknown when you call your friend using LINE Out for the following reasons.
1. Restrictions may be in place on the recipient’s device
If the recipient of a call is using NTT docomo or Softbank, the call will appear as Unknown or Private on the recipient's device.
Caller ID functions differently depending on the recipient’s device. Some devices can display the caller’s name as it is saved in the device’s contacts, while others may display the number in international format or as Unknown.
2. You did not verify your phone number
If you do not see a phone number at the top of the page when you go to Call > Settings, you have not verified your phone number. In this case, your number will be displayed as Unknown when you make calls.
Please see the following article about how to verify your phone number.
3. You are using a data-only SIM card that cannot receive SMS messages, or an iPad, iPod touch, or tablet
You need to verify your phone number in order to use LINE Out. Devices that do not have phone numbers, such as iPads, iPod touch devices, and tablets, cannot be used with LINE Out. Data-only SIM cards that cannot receive SMS messages cannot be used to verify your phone number by SMS, so LINE Out also cannot be used with them.