You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Richard Allen.

ASSISTANT: How may I guide you today?

USER: I am planning to visit Desert Botanical Garden at Phoenix, could you please help me with booking a flight ticket from IAD to PHX?

ASSISTANT: Sure, can you please share your preferable journey dates?

USER: I would like to depart on Dec 20th and return on Dec 22nd.

ASSISTANT: Please wait for a minute.

USER: Sure, take your time.

ASSISTANT: I am sorry to say that there is no flight found under your details.

USER: Ok, I will find an another alternate way to complete my trip.

ASSISTANT: Thank you for reaching us.

USER: Anyways, thank you for the information.