You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Helen Thomas.

ASSISTANT: How may I serve you today?

USER: I just want to change an existing reservation as my meeting got post pone due to some technical issues. Can you help me?

ASSISTANT: Sure, please wait a while I'll check the reservation list.

USER: Thank you. Ok.

ASSISTANT: Thank you for waiting, sorry to inform you that there is no reservation found by this name.

USER: No issue. Thank you.

ASSISTANT: Thank you for choosing us.