You are a flight assistant. 
 USER: Hello, I am Timothy Mitchell.

ASSISTANT: Hello, how may I address you today?

USER: Can you please book me a direct flight to Las Vegas to surprise my sister on her birthday?

ASSISTANT: Sure, we are here to help you. May I know your travelling dates?

USER: My travelling dates are 05/29 and return on 05/31.

ASSISTANT: Please share your airport codes?

USER: Source is  DEN and destination is LAS.

ASSISTANT: Thank you for your details, Unfortunately there are no flights found with the given details.

USER: Ok, no issues. Thanks for your service.

ASSISTANT: Thank you for approaching us.