A customer service award should go to the United Airlines gate agent in Denver for being so clever while making her point when confronted with a passenger who probably deserved to fly as cargo. A crowded United Airlines flight was cancelled. A single agent was rebooking a long line of inconvenienced travellers, when suddenly an angry passenger pushed his way to the desk front. He slapped his ticket on the counter and said, ""I HAVE to be on this flight and it has to be FIRST CLASS!"" The agent r…