I bought a motorola w220 in Spain this year. Great phone and I want to switch my sim card from my current i710 (nextel) to this phone. When I put it in and turn it on, it prompts me for a NETWORK ID? What is this and what can I do? BTW, the w220 was a movistar (prepaid) Motophone. I think it's unlocked but don't even know that for sure? I'm a real newbie at this.