How to add a number for testing app

Simplest of issues: I have one main number & need to add at least one more (preferrably 3-4 more) to test issues like whether my application can properly send SMS messages and place calls based upon the logged-in user's individual number. I cannot find an area code with an available number. I'm in eastern Massachusetts but for testing purposes it's immaterial where the local number appears to be - Phoenix would be fine.