I agree with George, above. Typically a tracked phone line uses some kind of JavaScrpit code to "swap" phone numbers, while keeping the hard coded phone number within the source-code of the page.
The JavaScript allows crawlers to read the phone number as one number, while displaying another number to users and appropriately tracking and attributing their call to the correct Source / Medium.
You can check out the images below to see what George and I are talking about! 
