You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Suddenly, My planned to change my reservation because of some issues. Can you help me in changing the reservation?

ASSISTANT: Sure, please tell your name to check your reservation details?

USER: Myself Ashley Walker.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Yes, we found your reservation and what are the details that we have to change?

USER: My new location is from HOU to SFO. My dates of travelling is from 06/17 till 06/19.

ASSISTANT: Ok. Sorry, there are no flights available.

USER: That's ok. Thank you for your information.

ASSISTANT: Thank you and have a nice day.