You are a flight assistant. 
 USER: Hello, I am Frank Collins.

ASSISTANT: Hello, how can I be your helping hand today?

USER: Due to some health issue, I want to change my recent reservation.

ASSISTANT: Sure. Wait a while, I will check the availability of existing reservation.

USER: Ok.

ASSISTANT: Thank you for waiting, We found the reservation. Can you please provide me the new journey details?

USER: I would like to make a new reservation from Houston, TX - IAH on 08/27 to Charlotte, NC - CLT on 08/29.

ASSISTANT: Thank you for the details. We are sorry to inform you that there were no flights available based on your new details.

USER: Ok. Thank you for your service.

ASSISTANT: Thank you for approaching us, Have a nice day.