You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Gary Allen here.

ASSISTANT: How can I assist you today?

USER: My preferable dates for travel are 12/28 to 12/30. Can you reserve a flight ticket to Houston? The price limit is less than 200.

ASSISTANT: Sure, can you please help me with the airport codes?

USER: My airport codes for boarding the flight are BOS to HOU.

ASSISTANT: Let me check for the availability of flight.

USER: Sure.

ASSISTANT: Gary, there is no flight available at your request.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for contacting us.