You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am David Taylor.

ASSISTANT: How can I assist you?

USER: Could you please help me to change my reservation?

ASSISTANT: Yes, I am here to assist you. Can you wait a second while I check?

USER: Sure.

ASSISTANT: Sorry as per the reservation records there is no reservation been found on your name.

USER: Ok, not a issue. Thank you.

ASSISTANT: Ok, thank you for choosing our agency.