You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, can I know your name please?

USER: Ok, my name is Patrick Williams.

ASSISTANT: Ok, please wait for a while.

USER: Sure, I will wait.

ASSISTANT: Sorry Williams, there is no active reservation found with your name in our records.

USER: Ok, no problem. I will try with the any other travelling agency.

ASSISTANT: Most welcome.

USER: Anyways, thank you for your service.