You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you at this moment?

USER: Actually, I need to change an existing reservation, can you please help me out?

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Sure, my name is Samantha Wilson here.

ASSISTANT: I have found your reservation. May I know your travelling dates?

USER: Sure, My recent airport codes are LGA and SFO respectively.

ASSISTANT: Could you send me your planned trip dates?

USER: My planned travelling dates are from Oct, 28 and 30.

ASSISTANT: Ok, may I know your airline preference?

USER: I would like to fly with big brands airlines.

ASSISTANT: Sorry to say that, there are no flight's available based on your travelling dates.

USER: Ok, not an issue.

ASSISTANT: Thank you for approaching us.

USER: Thank you for your information.