A method may be performed by a sending mobile phone that transmits SMS messages and transmits packet switched messages via a PSMS. The method may comprise sending first information representing a phone number of a first receiving mobile phone and receiving a first response to the sending of the first information. After the first response is received by the sending mobile phone, an SMS message may be sent to the first receiving mobile phone, based on the first response. Second information representing a phone number of a second receiving mobile phone may be sent by the sending mobile phone and a second response to the sending of the second information may be received. After the second response is received by the sending mobile phone, a message may be sent via a WLAN and the PSMS, to the second receiving mobile phone, based on the second response.