The Knowledge Graph is sometimes hilariously inaccurate, but this latest update might help fix that. If Google recognizes you as an "official representative" of information contained within a knowledge graph box, you can suggest changes. An article in Search Engine Land details how to do it.
"If you search for something that brings up a Knowledge Graph box that is associated with your Google account, be it your biography information or maybe a company you represent, then Google will show you a box that lets you make changes. The box says 'is this info up-to-date?'"
How does Google tell who is an official representative? With your YouTube channel or Google+ page:
"If you officially represent a topic that has a Knowledge Graph card in Google search results, you can request changes to that card. To be recognized by Google as an 'official representative,' you need to be signed in as an owner of the topic's official website, YouTube channel, or Google+ page."
It's important to distinguish that this applies to Knowledge Graph boxes, but not to Google My Business information.