Check what your charge looks like on a bank statement before you change anything else. This is the highest-return thing in this thread and it is usually a one-field fix.
A large share of disputes filed as fraudulent are not fraud and are not even unhappy customers. They are somebody scanning a statement, seeing a name they do not recognise, and clicking the button their bank makes very easy. Your customer knows your product name; if the statement shows a company name, an old trading name, or an abbreviation, they have no way to connect the two.
What to do:
Set the statement descriptor to the name people actually bought from. The one on your website and in your emails, as closely as your processor allows.
Say it explicitly at checkout and in the receipt. One line telling them what will appear on their statement removes the entire category.
Send a receipt immediately, with the product name, the amount, and how to contact you. People dispute when they cannot find another route.
This also explains why generosity has not helped: the people filing are not weighing your refund policy at all. They never got as far as considering it, because they did not know it was you. A policy only works on people who know who you are.