You are a flight assistant. 
 USER: Hello, Jeffrey Thompson here.

ASSISTANT: Hello, how can I assist you?

USER: As I am a scientist, I want to attend science festival with my students at San Francisco. Can you do the reservation?

ASSISTANT: Ok, may I know your travelling dates please?

USER: Dates are 04/17 and 04/19.

ASSISTANT: What are your airport codes for this journey?

USER: I would like to travel from Denver, DEN to San Francisco, SFO.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, no flights for you on your requested dates.

USER: No problem, Thank you.

ASSISTANT: Thank you for reaching our assistance.