You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. May I know your good name Please?

USER: Sure, I'm Jacob Thomas. I want to change an existing reservation. Can you please help me out?

ASSISTANT: Nice to meet you Jacob. Sure, I am here to help you. Please wait for a minute, I will check the reservation details.

USER: Sure.

ASSISTANT: Thank you for your patience.

USER: OK.

ASSISTANT: I am really sorry for to tell you, I cannot find any reservation with your requirements.

USER: It's OK fine.

ASSISTANT: Thank you so much for contacting us.

USER: Thank you.

ASSISTANT: It was my pleasure, Have a nice day!.