You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. What assistance do you need from us?

USER: I need to change my current reservation due to urgent meeting, can you help me with that?

ASSISTANT: Sure, I will definitely help you with that. Can you please tell me your full name?

USER: I am Robert Collins.

ASSISTANT: I have found your previous reservation. Can you please tell me which details you need to change in the past ticket related to travel dates?

USER: My trip source and destination are from HOU to IAD.

ASSISTANT: Please tell me your travel dates too.

USER: My travel dates are 12/15 and 12/17.

ASSISTANT: Ok, may I know your preferred type of class for your journey?

USER: I am ok with any class.

ASSISTANT: Ok, is there any preference about connection limit?

USER: I need a connecting flight, and my depart time must be in afternoon.

ASSISTANT: Sorry to inform you that, there are no flights available which were departing in the afternoon time.

USER: That's ok. Thank you for your service.

ASSISTANT: You are welcome. Thank you for reaching us.