IPhone transferring carriers?

Ok, so my friend got an iPhone 5s from the apple store and chose Verizon as her carrier there a couple years ago. She got a new phone and she wants to give it to me. I have tmobile. Will it work? I've read that the 5s is unlocked due to Verizon policy. Also I've heard if you get an iPhone from apple it's unlocked. I've also seen people put a sim card straight in the iPhone 5s and it works. I need advice:/

I don't think it will work because T-mobile and AT&T cellular phones use SIM cards (GSM) while carriers such as Verizon and Sprint do not (CDMA). Verizon phones I believe have their phone numbers sort of built into them… If that makes sense.

IPhone transferring carriers - 1

The iPhone on top would be from Verizon, and the one on the bottom would be T-mobile. As long as you have a SIM tray you can transfer mobile numbers within GSM providers.

Yes just call tmobile and theyll as you for your imei which is like your radio identification behind your battery or on the settings in your phone then theyll activate it.