You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Myself Alexander Lopez from Los Angeles. I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me with that?

ASSISTANT: Just a moment please. I am sorry no reservation found on your name.

USER: Ok. Thank you for your positive response.

ASSISTANT: Thank you for choosing us.