When fixed dialling is turned on, you can only call selected numbers and do emergency calls. Incoming calls aren't affected.
Press the phone icon.
Press the menu icon.
Press More below the required SIM.
Press Fixed Dialling Numbers.
Press Enable FDN to turn on fixed dialling.
Key in your PIN2 and press OK. The default PIN2 is 0000.
Press Disable FDN to turn off fixed dialling.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.