You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: William Roberts here. I would like to change my reservation due to sudden plan change in the trip, as our friends planned to go some other place this time. can you please help me by changing the reservation?

ASSISTANT: Sure, please wait for a while Roberts. Unfortunately, no reservation matching with your details to change further.

USER: It's ok. Thanks for checking.

ASSISTANT: Thank you for contacting us.