You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: David Williams here.

ASSISTANT: David, what kind of service you are looking from us?

USER: Can you please help me out in changing my recent reservation? As my friends postponed our planned trip to some other dates.

ASSISTANT: As an agent, I will be happy to aid you with changing your reservation. Please wait for a moment, I will check your reservation status and get back to you.

USER: Sure, I'll wait for your response.

ASSISTANT: Sorry to say you David, I have not found any reservation under your name in our database.

USER: That's ok, thank you for giving the information.

ASSISTANT: You are most welcome and thank you very much for choosing us. Have a nice day.