SMS (short messaging service) messages, commonly called text messages or texting, can be sent internationally due to agreements made between mobile phone carriers to handle each other's messaging traffic. A message can be sent across international borders using the same networking which comes into use when you send a message from an AT&T cell phone to one on Verizon or Sprint. Your carrier may charge you extra to send or receive an international text message.
Determine the international country code for the cell phone you wish to text. For example, the country code for both the United States and Canada is "1". If the number you are texting has been written down starting with a "+" sign, the country code should be included already; the plus indicates that the number is already in an internationalised format. For example, (212) 555-1212 is internationalised as "+12125551212".
If the country code is omitted from the phone number, add it as a prefix to the number you are texting. This is the equivalent dialling "1" before a long-distance call from a landline; the "1" to place a long distance call is the same as the country code prefix used to make a call to the United States or Canada. If the number you are texting starts with a "0", drop it before adding the prefix. For example, the number 020 7925 0918 in London would become +442079250918, since 44 is the country code for the UK.
If you are using a GSM phone (such as AT&T and T-Mobile), you can enter the phone number in international format when you send an international text: for example, type "+442079250918". CDMA networks (such as Sprint and Verizon) do not automatically handle internationally formatted numbers, so use the international call prefix instead of the plus sign; in the United States, the prefix is "011", so you would text to "011 4420 7925 0918". Some CDMA phones may automatically convert internationalised phone numbers for you; contact your carrier for details if you are not sure which applies to your phone or network.