New ASUS Zenfone 4 8GB Dual SIM (Unlocked) A400CG 3G 4" Intel Z2520 1.2GHz White Zenfone 4 8GB (Unlocked) White Unlocked cell phones are compatible with GSM carriers like AT&T and T-Mobile as well as with GSM SIM cards (e.g. H20, Straight Talk, and select prepaid carriers). Unlocked cell phones will not work with CDMA Carriers like Sprint, Verizon, Boost or Virgin.