Google maps used to be the best mapping software available.
Google maps pulls its data from many third party sources including "Superpages" what used to be Verizon's yellow page knock off. The problem is that Superpages seems intent on placing incorrect data on a listing so as to spur the owner of the listing to purchase advertising. Also, users can go and edit a listing adding/removing information.
My company has 4 listings for one store in San Francisco. Only one of them has the correct data for that store.
In order to "claim" the listing you have to click on the link, select "Business Owner", make the edits and, if one of the edits is the phone number, you have to wait 2 weeks for a "postcard" to arrive in the mail so that you can verify you're the owner. The problem of course is that we have 28 locations, doing this for each location is ridiculous.