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When fixed dialling is turned on, you can only call selected numbers and do emergency calls. Incoming calls aren't affected.
Find "Fixed Dialling Numbers"
Press the phone icon.
Press the Menu key.
Press Fixed Dialling Numbers.
Turn fixed dialling on or off
Press Enable FDN or Disable FDN (depending on the current setting).
Key in your PIN2 (default is 1111) and press OK.
Return to the home screen
Press the Home key to return to the home screen.