What is an Unlocked GSM Phone?

How do you unlock a phone?

There a few ways that one can unlock their phone:

1. Contact your service provider and tell them that you require an unlock code for your phone. The provider may charge a fee, while others may do it for free after 90 days of service.
2. Many websites offer unlock codes for under $20. To receive your unlock code, make sure you have your IMEI number (often found below the battery). Simply searching "unlock phone code"

Which phones are currently popular on the SIMPLE Mobile GSM Network?

Samsung Galaxy S 4G, HTC MyTouch 4G, LG G2X, HTC Sensation 4G, HTC HD7, Samsung Sidekick 4G