An overlay is the addition of another area code to the same geographic region as an existing area code to increase the number of available telephone numbers.
You’ll need to enter the full 10 digit telephone number (area code + telephone number) for local area calls. The new calling procedure doesn’t change the price of local calls. Long-distance calling still requires entering 1 + area code + telephone number.
Note: You won’t have to change your existing area code or telephone number.