10-digit mobile phone dialing requirement coming to your locale in the form of a telephone number area code "overlay"?
Have some local (7-digit) stored phone numbers in your iPhone Contacts to which you will need to prepend your current area code?
This little App will save wear-and-tear on your fingers, do the job quickly and do it accurately!
Check the "before (far-left) and after (far-right)" screenshots above of my iPhone Contacts entry for the Apple Store on Higuera Street in downtown San Luis Obispo, California. They tell the whole story - in pictures!