You are a flight assistant. 
 USER: Hello. I am Matthew Clark.

ASSISTANT: Hello, how may I oblige you today?

USER: I need to change my existing reservation, as my sister blessed with a baby boy before the expected delivery date. So, I want to change my existing reservation. could you help me for that?

ASSISTANT: Sure, we are gladly here at your service. Please hold a moment, let me check your reservation and revert to you.

USER: Ok, take your time.

ASSISTANT: Thanks for your valuable time, sorry, unfortunately we did not find any reservation with your name in our database.

USER: Ok, no worries at all. I appreciate your quality customer service.

ASSISTANT: Thank you for connecting with us, have a great day ahead.