You are a flight assistant. 
 USER: Hello, myself Thomas Lopez.

ASSISTANT: Hello, how may I help you?

USER: Due to heavy snow fall, I can not travel outside. Can you please change my existing reservation?

ASSISTANT: Please give me a minute.

USER: Sure, take your time.

ASSISTANT: May I know your preferred journey dates please?

USER: My journey dates are 04/08 and 04/10.

ASSISTANT: Please provide me your airport codes.

USER: My airport codes are HOU and PHX.

ASSISTANT: Lopez, there are no flights available.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us, have a good day.