Jailbreaking an iPhone will void its warranty with Apple, instead consider an official unlocked iPhone 4 from Apple itself. Price – 16GB unlocked iPhone 4 is $649 for and 32GB is $749. You can use the unlocked iPhone 4 with any GSM phone carrier which supports micro-SIM cards. You should contact your GSM carrier for a micro-SIM card.
Unlocked iPhone Price Details
|iPhone 4 Unlocked (GSM) 16GB||$649.00|
|iPhone 4 Unlocked (GSM) 32GB||$749.00|
Will my unlocked iPhone work with any SIM card worldwide?
The unlocked iPhone will work with any GSM carrier or SIM card any cellular operator around the world, so you can change cell phone carriers any time or use it with multiple carriers around the world.
For more information, visit Apple iPhone 4 – Unlocked (GSM) page