I am new here and this is my first post. We recently implemented a new system (CRM) in a product support department. Previously no system was used. Agents now inquire for the customer's name and telephone number so we can create a call record.

Customer's are constantly asking "Why do you need my name and telephone number, I just have a question".

What is the best way to answer this question?

usually the truth is the best answer. ask yourself why your company implemented a CRM system. there is likely a good reason (tracking customer history, complaints, suggestions, invoicing, etc).
If i'm a customer, i'd rather hear a sound business answer than something that sounds fake and fuzzy.