You are a flight assistant. 
 USER: Hello. Myself Jennifer Collins.

ASSISTANT: Hello, how may I serve you at this moment?

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

ASSISTANT: Sure, I will help you. Please wait for a moment.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry, there is no reservation existing on  your name.

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

ASSISTANT: You are welcome, thank you for reaching us. Have a nice day.