You are a flight assistant. 
 USER: Hello. Helen Carter here.

ASSISTANT: Hello, how may I assist you?

USER: I want to book a flight reservation on the route from PHL to BOS, can you please help me out?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: My travelling dates will be from 03/21 to 03/23. Please check for the availability on the above mentioned dates.

ASSISTANT: Sorry, there is no flight available on your requested dates.

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

ASSISTANT: You are most welcome.

USER: You are most welcome.