In the Sponsor Center “Advertise Here” link, this benefit is listed for sponsors:
“Depending on what city your business is located in, there’s a good chance there will be other teams within 25 miles of your business on the TeamUnify Ad Network.
When these teams are present, you’ll see them listed in your private ad account and your ad will automatically appear on each respective team website. The net result will be increased new customer reach and visibility without additional cost.”
So what happened is some business sponsored another team, your team happens to be within 25 miles of that business, and thus their ad appears on your site too.
It rarely happens, but if a conflicting or inappropriate ad appears on your site, email firstname.lastname@example.org with what ad it is and we’ll discuss either removing it or turning off the Sponsor Center for your team.