T-Mobile or Unlocked?

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So my buddy just sold me his iPhone 5S. I own an iPhone 4S with Sprint. Is there anyway i can get a micro sim from Sprint and use it with that? Or i would be open to getting a T Mobile plan also...i'm not sure if the phone is unlocked or purchased from T-Mobile...there was no micro Sim Card in it when he sold it to me.

Any help is greatly appreciated!