You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Kathleen Lopez.

ASSISTANT: What type of service do you want from our travel agency?

USER: Could you please help me to book a ticket to Denver with a normal-cost?

ASSISTANT: Sure, I will search the flight for you. Can you please tell me your source and destination airport codes?

USER: My source and destination airport codes are DTW and DEN.

ASSISTANT: Ok, on which dates you are willing to travel?

USER: I want to start on May 10 and return on May 12.

ASSISTANT: Ok, do you have any class preference?

USER: I don't have any class preference.

ASSISTANT: Sorry to inform you that, I have not found any flight in the normal-cost airlines on the dates you have given.

USER: No problem, thank you for the information.

ASSISTANT: You are most welcome. Thank you for reaching us.