Your default sending country determines how your mobile numbers are validated, as well as which international prefix is automatically added to the front of any contact numbers added to the recipient field or contact profiles (unless a prefix is already present).
1. To change the default sending country, go to the menu and click on the Profile icon, then select Profile:
4. Under the My Details heading, find where it says Default Sending Country and select from the dropdown menu.
5. Now click Save on the bottom right and you're done.