Will AT&T unlocked a used iPhone 4S bought elsewhere?

So, I'm looking to pick up a used iPhone 4S for myself soon, since lots of people are selling theirs now that the 5 is out. What I want to do is get an AT&T unlocked phone to then use on the t-mobile network. But I've noticed that used factory unlocked phones cost $50 to $100 extra over a locked phone. So my question is, If I go buy a used 4S from craigslist, ebay, etc, that's no longer on contract but is still locked, would I be eligible for AT&T to factory unlocked the phone? Would they do that for me? Or will they refuse because I didn't buy it new from them?

Added (1). I know that there's other ways to unlocked an iPhone, but I really want it to be FACTORY unlocked, so it can still take any new updates and things like that

Do I need to remove sim from iPhone 5?

I bought a Verizon iPhone 5 for someone international. I bought it contract price and will pay ETF fee. Do i need to open the phone and remove sim after cancelling or I can just send phone sealed in box and it will automatically be non contracted?

Added (1). Amanda, the VErizon iPhone 5 is global. Whether it has a sim card or not, there's a slot on iPhone 5 for micro sim card

Why is Belkin Wi-Fi on iPhone not working?

In settings it says that I have got the network and am logged in but in the top left hand corner it shows the mobile data symbol not the normal Wi-Fi one. I stopped using mobile data (lost signal) but when I tried to use Internet it said something along the lines of the webpage failed to load because safari is not connected to the Internet.
This is really annoying and it is costing me loads to write this!

Will a blackberry sim card work in an iPhone 4 if we cut the sim?

My friend has a blackberry and wants to buy an iPhone 4 off someone he knows. I have a micro sim cutter that I used when I went from iPhone 3G to iPhone 4. If we cut down his sim it will fit in the iPhone, but will he still be able to use Internet and call people? Also, would his network provider be able to send him a new iPhone sim but with the same tariff? Cheers

Screen on the Iphone 4s?

I'm into repairing Iphone, Iphones, because when my Ipod broke I fixed it by myself.
This is an Iphone 4s from AT&T
It was dropped (looked like someone nuked it haha) the screen is cracked, the back is cracked even worst, and I opened it up and the hardware was completely perfect
It won't turn on when I plug it into the computer, maybe it's dead and I'm inpatient, and the screen remains black no matter if I try a hard reset or anything else.
I ordered a new screen, going to try and open it up and replacing it to see if that helps.

My questions is: If it's not the screen, and nothing is wrong with the mother board or any other part, what could be wrong with it? Perhaps the battery?