You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

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

ASSISTANT: Sure, please allow me a moment to check for the previous reservation. May I know your name please?

USER: Ok, I will wait. Sure, my name is Angela Roberts.

ASSISTANT: Angela, there is no reservation found under your name.

USER: Ok, that's fine. Anyways, thank you for your service.

ASSISTANT: Thank you for contacting us.