Can I use a new iPhone 5S with AT&T if I'm on contract?

So a while back I broke my iPhone 5S. So I just sold it on ebay for parts and I think I'm going to buy a brand new iPhone 5S off of ebay. The one I want is brand new and never been used or activated. If I'm still on contract from my old iPhone 5S, can I use this new one that hasn't been activated? I may already know the answer but I just don't want to buy it and have something go wrong.

Added (1). The brand new one on ebay is an AT&T iPhone. Will it have to be factory unlocked in order to work? Or is it good to go and I can just take the activated sim card from my old 5S and put it in this new one?

Did i overcharged and damaged my iphone battery?

I accidentally charged my iphone overnight for about 12.5 hours. I forgot to put the timer for the charger and accidentally charged my 4s for too long. My question is did that charge ruined/ damaged my iphone battery? I heard that li-ion battery can stop the charge after the device is full. Does the 4s have li-ion battery?

How to reset iPhone to default?

I recently broke my iPhone so my mom got me one from someone at her work who no longer works there. I tried to reset my phone through settings>general>reset>erase all content and settings. Which went smoothly until it prompted me for the previous owner's Apple ID password which I have no way of finding out… Help?

Unlocking iphone 4 via jailbreak?

Is there any jailbreak out for ios 7.1 that can unlock my iPhone 4 or enable it to use any carrier for free? If anybody could point me in the right direction or knows if it is possible to do this I would really appreciate if you took the time to help.<3

Added (1). i want to do this for free if possible

I accidentally deleted a story on iPhone?

I have these periods where I love writing, and then periods where I don't, this is an on period. The stories I wrote are usually fanfiction, I had a story around 10,000 words. I had just finished it, and I went to copy and paste it with another note, I ****** up and accidentally deleted it.

I know it's not actually a question, but I'm so upset. I had just *finished*, and now I'll have to start over.

Has this happened to anyone else?

My iphone is not recognized in itunes?

I plugged in the USB of the iphone and its connected but its not turning on or anything.

The lock button is broken so i can't turn it on by pressing it.

i tried restoring it the first time but it said i didn't have enough disk space, so i cleared it and it still didn't work

Then i updated the itunes and its not even recognized at all. I can't click restore because its not shaded in black its grey so its un-clickable.