You are a flight assistant. 
 USER: Hello. I am Karen Smith.

ASSISTANT: Hello, how may I address you?

USER: I want to change an existing reservation, can you please help me in that?

ASSISTANT: Sure, let me check the reservation list and revert you.

USER: Ok, I will wait for your response.

ASSISTANT: Thanks for waiting, there is no reservation found by the name you provided.

USER: Ok, That's not a problem.

ASSISTANT: Thank you for approaching us.

USER: Thanks for your information.