You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?.

USER: Brandon Lee this side. I want to change my existing reservation, due to some health issue. Can you please help me?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please wait for a second, I will check and get back to you.

USER: Ok, take you time.

ASSISTANT: Thanks for waiting, there is a reservation found on your name. Can you help me with your new journey details?

USER: Sure, my new airport codes are from SFO to DFW.

ASSISTANT: Please share me your travelling dates?

USER: My trip dates are from 04/11 till 04/13.

ASSISTANT: Please wait for a while.

USER: Ok, take your time.

ASSISTANT: Thanks for being on hold. Sorry for the inconvenience, there is no flight found with your needs.

USER: It's ok, thank you for checking.

ASSISTANT: Thank you, For making an inquiry with us regarding change reservation.