A mobile phone includes at least two subscriber identity module (SIM) cards. The mobile phone queries a number portability database (NPDB) for at least two telecom operators of the at least two SIM cards. The mobile phone queries the NPDB for a telecom operator of an outgoing number dialed using the mobile phone. The mobile phone selects one SIM card with one telecom operator same as the telecom operator of the outgoing number from the at least two SIM cards.