Phone numbers have a basic structure to them, although the exact structure actually varies between countries.
Inside your own country, the country code is not necessary and phone numbers are entirely unique.
This is done to allow phone numbers to remain accurate when sent to foreign recipients.
you might manually configure the default country code though if you go to Gmails parameters.
press the cogwheel icon, then on See all tweaks.
snag the country whose country code you want to be used by default, then stash your changes.
