Currently number porting only works for French onoff numbers, but full support will be coming soon!
To port your number into the onoff app, simply select 'number porting' from the main menu.
You will be asked for your phone number and RIO code, as well as the date you'd like your number to be ported at.
The RIO code is given to you by your network operator.
To port out an onoff number, simply dial 3179 with the onoff number you wish to port; an automated message will tell you your RIO code, and also send it to you in a text message.
You can now provide this code to your new telecom operator.