If you have an active sim card then just insert it and use the phone.
Samsung Galaxy S5 16GB Black Unlocked (SM-G900A) AT&T
Samsung Galaxy S5 G900A 16GB Black 4G LTE GSM Unlocked -Used
Samsung Galaxy S5 16GB - Unlocked AT&T T-Mobile Smartphone - All Colors
Samsung Galaxy S5, White 16GB (AT&T)
Samsung Galaxy S5 G900V Verizon 4G LTE Smartphone w/ 16MP Camera - Black - Verizon
Samsung Galaxy S5 G900V Verizon 4G LTE Smartphone w/ 16MP Camera - Blue - Verizon
