You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Richard Davis here.

ASSISTANT: How could I help you?

USER: Due to sudden health issue, I am unable to travel in a flight on those dates. Can you please help me out with changing of my reservation to another date?

ASSISTANT: Sure, just a minute please.

USER: Sure, take your time.

ASSISTANT: I am sorry no reservation found in our database, might be there is an issue while doing reservation.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for utilizing our service.

USER: Most welcome.