Hello.
Hello, how may I help you at this moment?
I am Helen Williams. Can you help me in changing my previous reservation?
Sure, I can help  you with that. Please give me a moment to check your previous ticket.
Sure.
Sorry to tell  you, there is no previous ticket found on your name to modify.
It's fine. Anyway, thank you for your help.
It's my pleasure to help you. Thank you for choosing our services.