A:AnswerDon't really know. Always bought from ATT prior so didn't know anything about locked/unlocked phones or what that meant. First encountered when I looked at various phones, new and used, on the internet. I now believe it to be the case that all ATT phones are locked meaning they will only work if you have ATT as your service provider. Don't know anything about other service providers like T- Mobile.
A:AnswerYes they can but i don't know if they will do it for you. You can ask. I did it myself. I simply transfer my sim card to the new phone and let the cell update. I had no problems and i didn't notify tmobile.
A:AnswerNo you don't need to be on a plan. If you scroll down you will see the price if you buy the phone with a plan and the price of you don't want a plan.