OnePlus How to enable or disable "Fixed Dialing Numbers"

The phone app on the OnePlus smartphone includes a feature to set up a call restriction and allow only specified phone numbers to be called or to make calls themselves.

This function serves as a safety feature when setting up a smartphone for children, for example.

After successful activation the allowed phone numbers can be entered in the same menu item.

Note: In order to FDN, the PIN2 is required, which can be found in the documentation of the SIM card.
Otherwise please contact the network provider support.