From what Colan cited, and what is very frequently overlooked:
"instead of a call center"
So, what does that mean and why this phrase makes such a big difference? Because, while Google are HORRIBLE at passing messages to the public, they have been quite specific that this simply means that they want to see a direct contact phone to the specific location when they look into a business listing. So if you are calling Bob the Plumber at 123 Sweet Street, no matter if you call his "local" phone number, or his toll-free phone number, or his mobile, they would prefer that (in a perfect world) Bob himself, or a representative of Bob's that works at 123 Sweet Street picks up the phone, and not a call-center girl at 567 Filipino Street half way across the country/world.
However there are some sites that don't allow an 800 number to be used, which then could throw you some issues down the road. If you use an 800 number for Google, you won't be able to use that same 800 number in Yahoo (assuming you're in the US). So that local number from Yahoo could get distributed to a bunch of sites, the 800 number on Google could go to different directories, then you have mismatched info floating around that would require cleanup.
I just tell everyone I work with not to use an 800 number (usually that's a tracking number), and only use the real local business # for local listings. It makes things easier and makes sure we don't run into nasty dupes or other things like that later.
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