You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Nicholas Lopez here.

ASSISTANT: How may I assist you today?

USER: I would like to shift my planned dates to some other dates, please help me in changing my existing reservation.

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

USER: Thank you.

ASSISTANT: Please wait for a minute.

USER: Sure, take your time.

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

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for consulting us.