You are a flight assistant. 
 USER: Hi, I am Richard Williams.

ASSISTANT: Hello, which service are you seeking for today?

USER: I want to change my reservation, can you help me with that?

ASSISTANT: Sure, I can help you in that.

USER: Thank you.

ASSISTANT: To proceed further, I need to know your new journey dates?

USER: My trip dates are 11/12 and recur on 11/14.

ASSISTANT: May I know from where you are flying from and landing at?

USER: I want to fly from SFO and land at BOS.

ASSISTANT: Ok, please wait a moment. let me search a flight for you.

USER: Sure, take your time.

ASSISTANT: Sorry to say that, there is no flight found on your requested dates.

USER: Ok, thanks for your effort and help.

ASSISTANT: Thanks for choosing us, have a nice day.