How to set an empty number for a mobile phone?

The method of setting the mobile phone to an empty number is as follows:

Mobile phone: Huawei P40.

System: EMUI 10. 1.0.

Tool: Dial key.

1. Turn on the phone and click "Dial".

2. Enter "* 2 1 * 1380000000 #" and click "Dial".

3. If "Call Forwarding Registration Successfully" is displayed, click OK. If someone calls you at this time, the number displayed will be empty.

4. If you want to turn off the display of empty numbers, just enter "#2 1#" and click "Dial".

5. Display "Call forwarding service has been disabled", and then click OK. At this point, the normal display function of the mobile phone has been restored.