Many local business owners are surprised with the information that appears when they (and their customers) come across their business listings at Google and Bing. Often, incorrect or out-of-date information shows up with no explanation about where it comes from.
In some cases, even business owners who have already claimed their listings at major search engines like Google and Bing continue to see improper information displayed about their businesses, which understandably just adds to their frustration.
The reason this happens is that these search giants pull in business information from a variety of other sources, in addition to maintaining their own business databases. They both do the best they can to match the data that comes in from these other sources with what they have in their own index, but sometimes that doesn't happen properly.
If the information is different enough from the correct listing, search engines might think it's a different business—or they might even feel that the wrong information appears so many times in the other places from which they get their data that the info might actually be "right."
The sources that Google and Bing pull information from vary from country to country. Each has its own set of important players, known as data aggregators.
These aggregators have typically accumulated their business databases by scanning and transcribing things like phone records, utility records, business registration websites, and printed yellow pages directories.
Google also crawls the web looking for business information wherever it can find it: online yellow pages directories, review sites, local newspaper sites, and blogs. Many of these sources get their information from the same aggregators that Google does—just one more reason you need to make sure your business information is correct at those handful of primary providers in your country. If your data is wrong at those aggregators, it's likely to be wrong in many places across the web, including Google.
Even for experts, the local search ecosystem is incredibly confusing! But hopefully browsing the local search ecosystem graphic relevant to your country will give you a better understanding of how these local data sites fit together, and identify places to clean up incorrect listing information you might not otherwise have known about.