You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my existing reseravtion.

ASSISTANT: Ok, please wait. May I know your name?

USER: My name is Lisa Collins.

ASSISTANT: Sorry, no reservation found on your name to change.

USER: No worries, may be I booked from another travel agent.

ASSISTANT: Thank you for reaching us.

USER: Thank you for checking it.