You say they are coming to your locations. If those locations are actually owned or leased by you, they can't do this--it would be trespassing, and you could contact the police. But if they are coming to locations on public streets, then they can do this, subject to any regulations, ordinances, etc. by your municipality about where a bus can stop--you can't exclude them from public streets. Or if they are going to businesses or housing complexes you serve, that's up to the owners of those locations--they can let them come to their property or not. So all you can control, unfortunately, are locations owned or leased by you.