Refunds are a fact of life. They happen in almost every business to a greater or lesser extent, even when no refund option is given.
How you deal with them affects your customer relationship and therefore affects your business.
The first thing to remember is that it’s almost certainly nothing personal.
You can’t please all of the people all of the time.
For instance, my products vary in style but are usually “how to” products or “watch while I do this” products.