You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you?

USER: I am Raymond Williams. I need to attend a function in Philadelphia on 10/28. Will you please help me to get a flight ticket?

ASSISTANT: Ok, can you please provide your source and destination airport codes?

USER: Sure, airports codes are IAD and PHL.

ASSISTANT: Can you please mention your return date for booking flight ticket?

USER: My dates of travelling are 10/26 and 10/28.

ASSISTANT: Ok, please wait a moment, I will inform you.

USER: Sure.

ASSISTANT: Sorry to inform you no flights available as per your requested dates.

USER: Oh! It's ok. Thank you for your help.

ASSISTANT: You are welcome Raymond Williams.