To change the identity document associated with your idCAT mobile (NIE to DNI) you will have to go in person to request the deregistration at an ER idCAT mobile and later you can process the deregistration with the new document.
To modify your data, go to " Manage your mobile idCAT " and select the option according to your case:
If you have access to the mobile number with which you registered, press the option "Modify my mobile idCAT" and identify yourself.

Once inside you can modify the following data:
- Mobile number
If you don't have access to the mobile phone you signed up with, you can unlink the mobile number
Any of these procedures can also be done in person, consult the Mobile idCAT Registration Entities of the Generalitat of Catalonia (OAC's of the Generalitat) where you can make the modification immediately, or at any other Mobile idCAT Registration Entity where processes the request to apply the modification.