You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Charles Wilson here.

ASSISTANT: How may I help you?

USER: Actually, I am looking for a direct flight because of emergency, so can you please help me out with booking?

ASSISTANT: Sure, I will help you in booking.

USER: Thank you.

ASSISTANT: May I know your travelling dates?

USER: Sure, I am planning to go on 05/20 and please book a return ticket on 05/22.

ASSISTANT: Can I know your airport codes please?

USER: Sure, I want to travel from DFW to SFO.

ASSISTANT: Ok, please wait a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there are no flights found on these dates.

USER: Oh! So sad to hear. Anyway, I will choose another alternative to go there. Thank you for the information.

ASSISTANT: Thank you for choosing our services.

USER: Welcome.