Need help with gxp2000 & useranddevice setup

im setting up a new & lates freepbx. i turned on devices & user because my users have real phones and softphones.
so i have created user extensions like 7000-7100 and hardphones / devices like: 119000-119999.
now, whenever i get a registrations done on a gxp2000, it shows me the device id on the display, but i want the user extension. ( i could abuse the display name field, but the device id (eg 11999X ) is always on the display. how can i fix this? (the wiki says userextension and device id should be different)