In March of 2009 I bought a Blackberry from Cincinnati Bell. I just got through buying an iPhone from AT&T and switching my wireless plan to AT&T. I would like to sell the Blackberry but I don't know if it is compatible with any other system beside Cincinnati Bell. Can it operate on another system, say T-Mobile? I would like to be able to present it as being usable on another carrier. Thanks in advance for your input here.