You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: Mary Johnson here. I would like to travel from DCA to SFO, can you help me?

ASSISTANT: Sure, I will help you with that. Can you please provide your planned dates of travelling?

USER: I want to travel on 01/23 and 01/25.

ASSISTANT: Please wait a moment to check the flights on your route.

USER: Sure.

ASSISTANT: We regret to inform you that there are no flights moving to your region with your planned dates of travelling.

USER: Oh! not a problem.

ASSISTANT: Thank you for reaching to our services, hope you have a great day.