Reserve Slot Error

My Team Fortress 2 team offers something called a reserved or reserve slot whereby one can purchase guaranteed access to a server like knowing you can always get a seat at your favorite restaurant.   A fellow purchased one and then shot me a message that it wasn’t work.  I checked his credentials, verified his identity, and asked him to check again.  No luck.  I removed his slot and re-added it.  No luck.  I asked him what server he was trying to join.  He proved an IP address… for another team’s server.