don't you have a process implemented how to work with service request? There are many standards in this world one of them is ISO 20K ( ISO/IEC 20000 - Wikipedia, the free encyclopedia ).
And NCM is a tool to support or improve the processes. For example: Change Mangement but also Configuration Management (because you a database of your Configuration Items).
So my answer to you is: Ask for the implemented process ( I mean how they handle this service request before!) The manager have to answer this questions (how he implemented it or mentioned it)
have a nice day.
That sounds like a behavioral question to me. They want you to explain how you dealt with a situation where you were not able to meet the customer's request. Some things that come to my mind:
Were you able to come up with a compromise that satisfied the customer, maybe thinking outside the box?
Did you have to tell the customer no? Did they accept your answer? Or were they unhappy and you had to explain/convince them there was no option? How did you handle it?
There are resources online to help you understand behavioral questions along with recommendations on how to come up with your answers. Hope this helps. Good luck!