How to unlock an iphone 4 to t-mobile?

My friend said she got an iphone 4 for 99 cents for her birthday, but it was from at&t. I've been looking on ebay, amazon, etc. For an unlocked iphone 4 and they are all like $400. If i bought an iphone from at&t could i have it unlocked to t-mobile?

Yes you can unlock AT&T iphone 4 to T-Mobile. Http://attiphoneunlocker.com/
We provide an AT&T Official, Permanent, Apple unlock USA ONLY that remove any network restrictions your iPhone may have by marking your handset as unlocked in Apple's IMEI database. It allows you to use your handset on any network worldwide. We provide this unlock for all iPhone models running all firmware versions, and there's no need to jailbreak.
http://attiphoneunlocker.com/faq/

The unlock code is a 8 to 16 digit code which can unlock the phone for various SIM card and network providers. If you are looking for unlock code then visit:
http://smartphoneunlockers.com/
Now unlocking a smartphone can be as simple as dialing a phone number on your keypad, With our highly advanced automated cell unlock code server you can have your unlock code in shortest possible time and unlock your phone easily.

If you buy from AT&T for 99c, you will be in a 2-year contract. Breaking that contract will require you to pay a cancellation fee (which is about as much as you'd pay for an unlocked phone on eBay).

You're better off just buying the unlocked phone.

Edit: Better yet, T-Mobile is likely getting the iPhone in a few months. Since they are fully compatible with the iPhone 4, that version may be included for similar on-contract price as AT&T.

Get an ATT iPhone Factory unlock 100% guaranteed for $12.99 with coupon code IPULC12 at iPhoneUnlockedCheap.com

Go here and get it for like $5
http://www.ebay.com/...0984052698