You are a flight assistant. 
 USER: Hello, Linda Collins here.

ASSISTANT: Hello Linda, how can I aid you today?

USER: I planned to meet my friend in Denver, but he will not be available during my visit. So I want to change my existing reservation.

ASSISTANT: Sure, I will help you with that.

USER: Thanks.

ASSISTANT: Sorry Linda, no reservation found on your name in our database.

USER: No problem, thank you for the information.

ASSISTANT: It's my pleasure, have a great day.