You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How may I help you out?

USER: Can you please book a flight ticket with the name of Christopher Smith to Oakland, OAK?

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: On which dates, can I reserve you a seat?

USER: I am planning to attend for my brother's wedding on 05/26.So, I will start on 05/25 and return on 05/27.

ASSISTANT: Ok. Please share the origin place.

USER: Washington, IAD is my boarding point.

ASSISTANT: Ok, please wait, I will revert to you.

USER: Sure.

ASSISTANT: Thanks for your precious time, no flights found in search.

USER: It's ok, no problem. Than you for your information.

ASSISTANT: Thank you.