2.5. Dialing rules

In order to define the dialing rules for your softphone, open the settings menu of your Nsoftphone standard client by clicking on the symbol and select the tab "Dialing rules".     
The following dialing rule is set up by default in the settings of your softphone:

Activ: yes

Maximum length (internal telephone number): 5 
Access code (outside line): 0

Cut off the access code when calling: yes

This means that a "0" will be dialed as an outside line in each case the telephone number has more than 5 digits.
In case you have 3 digits internal telephone numbers (extensions), you would change the length of your internal telephone numbers to 3.