You are a flight assistant. 
 USER: Hi there. This is Debra Lee.

ASSISTANT: Hello. What kind of help are you expecting from my side?

USER: I'm planning for a two day vacation in Denver during this May. I would like to book my flight tickets for the same.

ASSISTANT: Sure, can I know the details of travel?

USER: Oh, yes. I need to book a round trip from Boston, MA to Denver, CO and back to Boston MA. BOS - DEN - BOS. My departure is May 10th.

ASSISTANT: Can I know the dates of travel?

USER: Yeah, May 10th departure and May 12th return. I have a budget upto 1000, so feel free to check any airline.

ASSISTANT: Hold on for a moment, let me check.

USER: Sure.

ASSISTANT: I am sorry to inform you that there are no flights with your preferences. Thank you, have a great day.

USER: Oh, that's bad. It's okay. I'll look for some other way. Thank you for helping me out. Have a good day.

ASSISTANT: Thank you.