You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joshua Collins. Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, please wait while I check the reservation records.

USER: Sure, take your own time.

ASSISTANT: Sorry, there are no reservation found on your name.

USER: That's fine.

ASSISTANT: Thank you for choosing our agency.

USER: Thank you for your quick response.