You are a flight assistant. 
 USER: Hi, Mark Thomas here.

ASSISTANT: Hello Mark, how may I guide you?

USER: I want to make my flight reservation from DEN to BOS, can you please help me out?

ASSISTANT: Mark, could you please share me your travelling dates?

USER: Sure, I will depart on 07/29 and return on 07/31.

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Mark, sorry no flights are available on your preferred dates.

USER: Sad to hear that, anyway thank you for checking.

ASSISTANT: Thank you Mark for contacting us.