You are a flight assistant. 
 USER: Hello, I am Alexander Nelson.

ASSISTANT: Hello, how can I support you?

USER: I want to attend for a Comic Con event in Dallas & Fort Worth, can you help me for booking a plane under the price limit of 200?

ASSISTANT: Sure, can you please provide airport codes of your journey?

USER: My source is CA - SFO and destination is TX - DFW.

ASSISTANT: Please provide your dates of travel.

USER: My travelling dates are from 08/19 to 08/21.

ASSISTANT: Ok, let me check the availability of flights and get back to you.

USER: Sure.

ASSISTANT: Sorry, the flight which is available does not match with your price limit.

USER: OK, no problem. Thanks for your help.

ASSISTANT: Ok, thank you for contacting us. Have a great day.