You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Charles Collins.

ASSISTANT: What can I do for you?

USER: I planned to spend free time with my friends in San Francisco city. Can you help me to find a flight?

ASSISTANT: Ok, can you please tell me your source and destination codes?

USER: Sure, currently I am staying in DEN I want to move to SFO.

ASSISTANT: Can you please provide me your travelling dates?

USER: My travel dates are 03/31 and 04/01. My budget is 500.

ASSISTANT: Sorry to say, no flights found on your details.

USER: Then, it's ok. Thank you for your information.

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