In order to access the Mobility setting, click on the "Mobility" tab (as shown in the picture below)




These are what the options within the Mobility tab will do:-

Enable Mobile Twinning- this will either enable or disable mobile twinning, this gives the user the ability to answer calls to their DDI on their mobile.

Twinning Number- This is where the user will set the number they want to have twinned with their extension number