Okay I have a Cingular L1400 LG phone and I wanted to get a different phone. I decided to buy a RIM Blackberry 7100t from ebay. It just got here today and I realized that its a T Mobile phone. My SIM card wouldnt work with it since I have Cingular and its T Mobile. Well my mom called the local T Mobile and asked if there was any way that it would work with a Cingular SIM card and the lady said that if it was unlocked that it should work. I was wondering if thats actually possible and if it is how can I see if its unlocked because it keeps saying Invalid SIM Card.