To use the menu, hit "up" , then "SEL" to open menu, should open in level 1, select MDL-SEL, hit SEL, will have the 10model screen displayed, select a new model Number using up/dn. Confirm the change - hit + and - together for 1sec. back out hitting "END".

You're prob not "confirming" your change - hold the + and - buttons down together for 1sec, should see screen kinda blink as it accepts change, then back out using end. If you're not getting there, its the confirm step - keep doing that step until you see radio acknowledge the model change. Believe takes longer to try and explain than to do it.