First time getting a dispute, how do I handle it?

First time getting a dispute for my SaaS.

I have evidence that they have used the product, they are disputing the second payment from the recurring subscription. Should I dispute or just accept or refund?

Any experience helps.

EDIT: Okay to give some more information, I don't care about the 8 bucks, and I'd have refunded if they ever reached out. But now there is also a 20 euros dispute fee if I accept it. And the user used the product, and then likely forgot to cancel the subscription and went this route instead.

Author: vadeconry