I don't upgrade phones very often, because I have 3 teenagers and have to buy them all the same phone or I'm in trouble. I have nextel from work and don't want to change that, so I need to stay with them. So in an effort to save money I was thinking of buying unlocked phones on ebay (maybe i850 or i855). Can I just take the exisitng sim cards from thier i730 and plug them in? Or do I need to buy new sim cards? Then how do I get them programmed? I tried searching for a while but can't seem to find the answer anywhere. Thanks for any help.