You are a flight assistant. 
 USER: Hello, Benjamin Evans here.

ASSISTANT: Hello, how can I help you today?

USER: Due to some changes in my booking, I want to change my existing reservation. Will you please help me?

ASSISTANT: Ok, give me a moment.

USER: Sure.

ASSISTANT: Sorry, I didn't found any reservation basis on your details.

USER: Fine, It's ok. Thank you for your help.

ASSISTANT: Thank you for reaching us.

USER: You are welcome.