If I unlock my iPhone, will that void my 2-year contract with AT&T?

I have an iPhone 3gs. I'm planning on getting the iPhone 5 very soon. If I were to unlock either of these devices on my own, would that void my contract with AT&T? Would I have to pay an early termination fee? I'm still going to use AT&T as my provider. I'm not planning on switching to any other provider. I just want to unlock my iPhone in the case that I ever go to a foreign country and want to use my phone with a different SIM card. I don't want to get in trouble though. I know jailbreaking voids your warranty with Apple, but will unlocking the iPhone cause any problems for me?

How to get iMessage on iPhone 3GS?

I'm at iOS 6 at the moment, when I first got iOS 5 I had iMessage for about 2 days then it just disappeared. I'm sure it's not there too. They say its built into the text app but for me it is not! I'm a little peved, anyone know what to do?

Will My IPhone Work in South Africa?

I have an I Phone 4 and I'm going to South Africa for two weeks. I want to text to my family and friends and occasionally make a call. My local AT&T store says my phone will work fine but they suggest a special program to permit more texting and calling at a cheaper rate but no internal modifications to the phone are needed. Want to make sure this is correct. Anyone traveled to SA with an IPhone?

New iphone 4s has no service?

I bought an iphone 4s from t-mobile this morning, however I have charged it fully and it says it has no service. I wasn't with t-mobile before so I understand the new sim could take a while to be registered but I'm worried there's a problem with my phone seeing as it's been 8 hours since I purchased the phone! Is having no service when you first get the phone normal?

My Iphone 4s froze while restoring?

Hi! So I needed to restore my IPhone 4s and my computer decided to restart itself while doing so and now it's stuck on the apple logo screen. When I open itunes, it doesn't even say my phone is connected to it so I can't resume the restoration.

How to switch regions on iTunes (iPhone)?

I've just updated my iPhone to iOS6 and wanted to update some of my apps. In the App Store and iTunes Store everything is now in dollars instead of pounds and its saying I can't update until I switch iTunes back to UK. I have no idea how to do this.

Unlock iPhone 5 legally for use abroad with Verizon? Calls with Verizon abroad

I'm not a permanent resident of the US but I'm going to buy an iPhone 5 from Verizon with a 2 year contract.
The problem is that I will have to go back to my home country in Europe in 10 months. I would like to know, therefore, if I can call Verizon during my contract to ask them to unlock the phone. Is that possible?

2nd question: since I decided to take a 2 year contract, it means that I would like to use my phone with Verizon abroad, meaning use my US sim card in Europe (because even when I'm back in my country, I will be paying $80 for the phone in the US, so I will have to use the credit there, otherwise it's a waste of money). I will mainly call the US from Europe. Will I be able to use my phone plan abroad?

I hope I was clear because it's a bit hard to explain.

Added (1). EDIT: If I decide to buy an unlocked smartphone, does it mean that i can take any straight talk card when I'm the US? I mean a SIM card with a US number attached to it (just like prepaid phones)

Can i buy an Iphone 5 in USA but use it in Brazil?

I want to buy an iphone 5 when i go to USA, and wanted to know when i get back to brazil will i be able to use it there? And by use i mean like iphone 4 and 4s there was a slot where you can insert a simcard so you can call in the country you moved or visited too. Please REPLY As soon as possible