Credit/refund of JR tickets?

We have changed our itinerary since purchasing shinkansen tickets to Kanazawa. We are now going to Kyoto instead. The trip to Kanazawa is this Thursday. Can I get a refund of the tickets or a credit towards the cost of the tickets to Kyoto? If so, how do I do this?
Thank you very much.

Yes you can get a refund. You can do it at the jR ticket office anytime before the scheduled departure of your train.

You are normally allowed one change of tickets for free. If more than this, there will be a small handling charge. If you want a refund and paid by credit card, it may be more difficult if you try to do this at a smaller station, better to go to the original booking station.

Thanks so much for the advice. Will get this organised tomorrow.