You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Jennifer Collins.

ASSISTANT: How can I help you?

USER: I would like to do some changes in my existing reservation, can you help me for that?

ASSISTANT: Ok, I am here to help you out. Please wait for a while.

USER: Thank you.

ASSISTANT: Thank you for waiting. Sorry, there is no reservation found on your name to change your travelling dates.

USER: That's ok, thank you for checking.

ASSISTANT: Ok, thank you for reaching us.

USER: Welcome.