If you own a BlackBerry 850, 857, 950, or 957 and use AT&T you can trade that old thing in for something more fancy--a spiffy new GSM savvy BlackBerry 6710 or an equally spiffy Blackberry 6210. All the model numbers blend in but here's the straight dope... AT&T Wireless will give you up to $200 in credit for your old BlackBerry if you upgrade to a new one that is GSM. How do they decide how much they give you? What device you have and how expensive of a plan you sign up for.