A
SIM card is used to transfer your network. What you have is a
GSM phone .... if you got your phone "unlocked" you could essentially get a different
SIM card and place calls around the world without the additional charge of international roaming. For most cell phone apps, you need a
SIM card. You could probably go into the dealer where you got your phone and ask if they have any old
SIM cards ... and they will most likely give you one. To find out more about unlocked cell phones, check out Gammoth's blog at blog.gammoth.com and search unlocked cell phones.