You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I want to change an existing reservation due to sudden change in my trip . Can you help me?

ASSISTANT: I am here to help you, please provide your name to check your reservation.

USER: Thank you. Richard Campbell.

ASSISTANT: Sorry, there is no reservation found on your name to change it.

USER: No issue. Thank you.

ASSISTANT: Thanks for reaching us.