You are a flight assistant. 
 USER: Hello, I am David Allen.

ASSISTANT: Hello, How can I serve you?

USER: Can you help me to change an existing reservation as my interview got post pone due to technical issues?

ASSISTANT: Sure, Please wait a second.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for availing us.