You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Stephen Lewis.

ASSISTANT: How may I help you out?

USER: I want to change my existing reservation, due to my health issue. Can you help me out?

ASSISTANT: Ok. Sure, I will check the reservation list and let you know.

USER: Ok.

ASSISTANT: Thanks for your time, no reservation is done earlier to proceed further. Thanks for choosing us.

USER: Not an issue. Thank you.