You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to book a flight to San Francisco from Boston, can you help me?

ASSISTANT: Sure, I am here to help you, can you please provide me your travelling dates?

USER: I will be travelling from 12/21 to 12/23, please check the availability on these dates.

ASSISTANT: Ok, may I know your name?

USER: My name is John Jones.

ASSISTANT: Ok, let m know your airport codes to search a flight for you.

USER: I will takeoff from BOS and returning from SFO.

ASSISTANT: Ok, give me a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no flight available for you.

USER: Oh! That's sad, thank you for checking.

ASSISTANT: Ok. Thank you for choosing us.

USER: You are most welcome.