You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Alexander Hernandez.

ASSISTANT: How may I help you?

USER: I would like to change my existing reservation, can you help me in that?

ASSISTANT: Sure, please wait a minute.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry Alexander, there is no active reservation found under your name in our records.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Most welcome.