asterisk users - Oct 2006 - cut ip adress from caller id number display (ci$co 7941)

I'm playing with phone ci$co 7941 with sip image (8.02SR1),
strange is, that phone displays caller id number with ip address of 
asterisk server like "8210@172.20.24.11"
I think, this is some bug in firmware, but I would like to find some 
workaround,
maybe using SIP_HEADER function, but seems, that this can be used only 
when calling from SIP to SIP,
i.e. not possible to use SIP_HEADER function when I call SIP phone from 
IAX channel:
Oct 18 12:34:22 WARNING[13242]: chan_sip.c:9307 func_header_read: This 
function can only be used on SIP channels.
any other idea, or tip to another firmware with correct behaviour? thanks
PJ