You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I am Alexander Smith, can you help me for changing my existing reservation?

ASSISTANT: Sure, I will help you. Please wait a minute.

USER: Ok, I will wait for your reply.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: Oh! It's ok, no problem thank you for your services.

ASSISTANT: Most welcome.