While the XP10 does support Dual SIMs, the SIM operation is controlled by the software on the device. The Unlocked EMEA/UK/Global and Unlocked North America versions support Dual SIM/Dual Standby (DSDS). With our other North America versions, only ONE SIM can be active at a time (DSSS). The XP10 will read the SIM card in Tray 1 first, and if there is a 2nd SIM in Slot 2, it will not be read.