So what actually happened is you gave Google your phone number for the specific purpose of publishing it so customers of your business can contact you, and forgot. You should update your post so people aren't misled.
And then one day then decided to publish the one I'd given them for an identity check... in search results. I don't yet know why.
Since it was published by you as public contact information for your business on Google, either a customer or one of the contractors Google employs to update phone numbers in Maps listings then added it to Maps.
My post was about the Business Profile one. Which started (seemingly randomly) containing the same phone number.