Switching USCellular phone to Tmobile

I have a Samsung R225 now, my friend has a Motorola V60 that he got from USCellular (now AT&T). His work gave him a new phone and they use Nextel so he doesnt need his Motorola any more. He said I could have the Motorola. The problem is, I'm not sure how to transfer my service from my Samsung to the Motorola.
Tmobile said as long as the phone is 1900mhz, GSM, and is unlocked that I can use it. I dont know if USCellular was GSM since they were taken over by AT&T.
They also said that the phone has to be unlocked, how do I know if the Motorola is unlocked? It is no longer serviced by USCellular.
Tmobile said if it meets all these requirements I can just drop the SIM chip in and it'll work.

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unfortunately, the motorola v60 is a TDMA phone, meaning it is a different technology than GSM, which is what t-mobile uses, so the phone is incompatible.