help needed with c12 and o2 sim card

high i have this problem i have old c12 mobile with a 02(btcellnet) sim in it were u top up with 15 pounds a mounth and it gives u free calls to 1 bt landline (wich i use to call sick aunt) problem is i wont to use this sim in my 5210 but the sim is tyed to the phone some how , i was wondering if anyone has managed to get round this , i have 1 idea i think it might be the imei they are using to lock the sim to phone and i was wondering if i just change imei on the 5210 to the phillips
imei will it then work??

any help would be nice

thannks in advance skedone

networks cant lock tim cards to imei's.

it sounds like your other phone is GID1 locked. some networks use this to stop contract users putting thier sim in a payt phone.

I may be wrong, but that what it sounds like to me.

Dinger :)

so if i use same gid code on the nokia the sim should then work in it?/