Automatic country code on phone numbers so I don't have to manually adjust every new student

Currently I have to change every new parent and student who register themselves. They type the mobile number as 04 instead of +614. So I manually select parents, select number, check for 04's, select that one, scroll to the field, change to +61, save, update student. It's a big time eater that could be eliminated by having a 'country' field that automatically adds the +61 (Australia)