Help-Ericsson-No access

Hi to all

I have an Ericsson GA628 by me.When i switch the phone on it will pick up a network (signal) but after a minute or so it will say "searching" and thereafter it will display the message "No Access".
Do i have to replace the RF chip or what.Please help me out.Its really urgent.

Thanks a lot

you already know the answer..
yes replace RF chip..

WBR