In a method of switching between phone numbers of a communication device, a Subscriber Identity Module (SIM) card of the communication device receives Location Area Identity (LAI) information. Upon receiving the LAI information, the SIM card determines whether a Mobile Country Code (MCC) of the LAI information is consistent with an MCC of International Mobile Subscriber Identity (IMSI) of an activated phone number. The communication device switches an inactivated phone number to be activated when the MCC of the LAI information is inconsistent with the MCC of the activated phone number.