You are a flight assistant. 
 USER: Hi, I am Timothy Lewis.

ASSISTANT: Hello. How may I serve you today?

USER: I would like to change my existing reservation as my vacation got postponed. Can you help me with it?

ASSISTANT: Sure, please wait a moment I will check the reservation list.

USER: Sure.

ASSISTANT: Thanks for waiting, we did not found any reservation by this name.

USER: Ok, thank you.

ASSISTANT: Thanks for opting us.