We have one customer who must dial 1+area code to reach our main number. We have a business account with a non-ported number. We are in the biggest suburb of Kansas City as is the customer. They are less than a mile from our office. They don't have to dial a 1-area code with anyone else in our area. It's a problem because their staff perceives it as a long-distance call and they have to get prior-authorization to make long distance calls. From what I can tell, their carrier is SBC.
We had the same issue with our new 470 area code here in Atlanta (a local call). Clients who have service with Comcast and Windstream have to dial a "1" where all other carriers in Atlanta do not. Test with another local carrier and see if that person has/doesn't have issues before confirming it is the "originating" carrier's routing issue.