You are a flight assistant. 
 USER: Hello. My name is Jessica Perez.

ASSISTANT: Hello, how may I guide you?

USER: I would like to book a flight ticket from PHL to BOS.

ASSISTANT: Ok, can I know your preferable dates?

USER: I will be travelling on dates from 09/21 to 09/23.

ASSISTANT: I am sorry, there are no flights available.

USER: That's ok. Thank you.

ASSISTANT: Thank you.