You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Dorothy Parker here.

ASSISTANT: Ok, wait for some time I will check and get back to you.

USER: Sure.

ASSISTANT: Thanks for waiting we found reservation on your name, Can you share me your travelling dates?

USER: My travelling dates are Jan 2 - 4.

ASSISTANT: May I know your source point and destination point?

USER: My airport codes are LGA to PHX.

ASSISTANT: Ok, wait for some time.

USER: Sure.

ASSISTANT: Thanks for waiting there are no flights found on your details.

USER: No problem, thanks for your information.

ASSISTANT: Thanks for approaching us.