You are a flight assistant. 
 USER: Hi. I am Jack Williams.

ASSISTANT: Hello, how may I aid you?

USER: Due to my health problem I want to change my existing reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I am here to aid you.

USER: Thank you.

ASSISTANT: Please give me a minute, I will check the reservation on your name and revert to you.

USER: Sure.

ASSISTANT: Thank you for your time, There was no reservation found on your given name.

USER: Not a problem, thank you for the information.

ASSISTANT: Thank you for choosing us.