HP ipaq 6818 SIM card problem

Hi all,I am new to this forum,hoping people here would reply for my question i am here I have got a HP ipaq rw6818 from US to india from one of my friends,i am not able get it connected to any network with indian SIM card,It would be great if i am let to know how i can proceed further, is there somethign i need to do to unlock to indian code or something ? btw, i called the HP customer care, they gave me a link of a ROM bios for my version, after i flashed that rom bios also i get the same error,the error is like, i get a "!" icon near the Tower symbol in my Mobile,meaning i am not getting connected, and i am not getting any operators in search that i do aswell.i tried with more than 3 different connections , i mean 3 different operator SIM card, the device reads the SIM contacts but not able to get connected,any suggestions and ideas would be much appreciated, thank u well in advance.regards