In our webapp, in the Settings menu item and the General tab, you will find the option to set a country code as default.
This means: If you enter a phone number without a country code, the code specified here will be used automatically.
Use this setting if you want to add your numbers in local format. If you are adding numbers from different countries, we recommend that you do not set a default country code, but instead make sure that the numbers are in the correct international format. If you do not want a standard country code, leave the field empty.
Example:
You create the number 0123 45678910 in your contacts, i.e. without a specific country code.
If you have set a German country code as default, i.e. 49, the SMS will be sent to the number
+49123 45678910
If you have specified a US country code as default, i.e. +1, the SMS will be sent to the number
+1123 45678910
If you have created the number as +49123 45678910, i.e. with a specific country code, the SMS will also be sent to this number, no matter what you have specified as a default country code.
An overview of all country codes can be found here: List of country calling codes(Wikipedia).
You can find more information about international SMS in our blog post about international communication.