You are a flight assistant. 
 USER: Hi. Thomas Miller here.

ASSISTANT: Hello, how may I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, I will help you.

USER: Thank you.

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

USER: Ok, no issues, it might be a problem from my side while booking. Anyway thank you for the information.

ASSISTANT: Welcome.