When i buy new iPhone what happens to older one?

I have a iphone which is under contract of At&t and 2 years are still remaining. If i get new iPhone 4s and when i transfer my old number to new iPhone will the contract terminate and transfer to new phone? How can i terminate the contract from old iphone with less trouble as possible and avoiding the ETF?

Added (1). I want to gift my old iPhone to someone

Damaged iphone4 exchange at apple store?

I'm wondering if apple store will exchange my damaged iphone4 for a new one. I heard that they take £120 and your old iphone and give you same 1- brand new. Is it true even if my iphone's screen and back side are very smashed… But still working.p.s. No insurance.

Why is my iPhone 4 messed up?

There, my iphone4 is only a year old and I got it brand new. It will connect to my Wi-Fi and then 30 seconds later the Internet won't work. It still says I have Wi-Fi on but it won't load and it has nothing to do with my connection because my iMac, laptop, ps3, and Xbox all connect perfect to it. And another thing. My iMessage is so messed. I'll send my friends who have iMessage and they all have iOS 6.0.1 a message and it says it sent and a phew minutes later ill giro the message an it will say sent as text. Even though when I sent it, it was blue. This happens a lot. And I've tried restoring my phone. I've rest the networks. I've rest my Wi-Fi. But nothing works. I have dropped my phone quite a bit but this has never happens before so I'm not guessing it has to do with anything on the j side. But it mite. And I mite cancel my phone and get a new one cuz it does has a cracked screen and should I get an iPhone 5 or galaxy s3?

I just jailbroke my iphone 4 on ios 6.0.1 and is stuck on apple logo

So i used redsn0w selected the 6.0 IPSW and it jailbroke successfully but its a tethered jailbreak i went to go do "just boot" the pineapple logo appears and then the apple logo appears and thats where it gets stuck! I've tried re-jailbreaking and it doesn't work so i'm out of ideas any leads would be wonderful thanks.

Iphone app similar to Pandora Radio? - 1

I currently live outside of the US, when i lived in NYC i used to always listen to Pandora Radio, but its not available out of the US. I was wondering if there may be a free app similar to Pandora that works outside of the US too?