could someone answer me this question. i bought a nokia3100 yesterday.i got it pay as you go.so i have an 02 sim.the phone is unlocked.i have an orange sim card with credit on it.so i put that in the phone.works o.k. but i have an o2 sim and new number.can i use that sim aswell in the same phone.ie take orange sim out .put o2 sim in.i take it i have to register the 02 sim? but will it lock the phone when i set up the o2 number? cheers for any help..