Call me back
Always respond to people who contact you by mail, telephone, or email (or anything else). Ignoring them is rude and gives the impression you don't care about them or that you are just lazy.
Answer questions as quickly as possible. Respond to both criticism and praise in a timely fashion. Don't ignore people because you disagree with them or the way they communicate.
Be courteous to people even if they are not courteous to you.
If you have to forward a message to the appropriate person, let the caller know you've done that. Don't just act like it's somebody else's job.
If you don't have the information a person has requested, tell them that, and say you'll get back to them when you have it.
Whether people contact events, businesses, government, or anybody else, they are entitled to a swift acknowledgement of their contact.