Hi emma,
You can buy Samsung epic 4G Touch from ebay.com or Amazon.com . I would suggest you to buy a carrier locked phone. Because, i have checked unlocked phones in ebay and amazon .(It indicates that your Samsung supports for all the networks without any restriction ) . The cost of unlocked phones are too expensive. Better, you can buy a locked phone and unlock it by using unlock code. You can get unlock code from any of the online service providers like [http://www.mobileunlocksolutions.com/samsung-epic-4g/rs16wp9/|Mobileunlocksolutions.com] to unlock it . Once, you have unlocked your5 phone from carrier lock, you can switch over from your current network to any other GSM networks .