You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I help you?

USER: Please change my existing reservation. I am Carol Hernandez.

ASSISTANT: Sure, please wait for few minutes.

USER: Ok.

ASSISTANT: Thanks for waiting. We found new reservation with your name, please share me your travelling dates?

USER: I will depart on 02/12 and will return by 02/14.

ASSISTANT: Can I know your airport codes?

USER: Sure. Origin is Houston, TX-IAH and destination is Houston, TX-HOU.

ASSISTANT: Please wait a minute.

USER: Ok.

ASSISTANT: Sorry there is no flight with your requirement.

USER: Thanks for the help.

ASSISTANT: Thank you for reaching us.