...failed"?and im using DiGi 4 now..? I just bought an unlocked nokia c3 & its a new original one! i'm using it with a prepaid DiGi sim card. The phone works for awhile and then it says sim card registration failed. then i have to take the sim card out and wait a while before i can put it back in to work. This happens constantly through out the day and it's really annoying. The phone is brand new. Why does it keep doing that? moreover, how to settle this problem?