Caller id issue of asterisk Ip phones when integrate with Nortel epbx

Hi,

Actually we have Nortel epbx which is now recently integrated with Asterisk pbx.Every thing is working fine but we have the issue for caller id.
We have configured the TIE between Nortel & Asterisk epbx.Suppose I wants to Forward the calls of one of my Nortel Phone to asterisk IP phone.And if I called that nortel extns from my mobile no. I observed that the call is landing on Asterisk IP Phone but the Clid should be My Mobile no. but instead of my mobile no its shows the no. 4877 4223 where 4877 is the CDN which is Mapped with Call pilot and 4223 is the one of the DN configured in Call pilot..Pls help me out to resolved this