How to forbid refund for in app purchases to Users

Is there any way to forbid refunding In App Purchases in my App. My app provides downloadable files/content when purchasing any item in App. But Users are taking refund and also they already get files Downloaded.

As I know refunds are valid for 15 minutes. Maybe you can enable your files to be downloaded after 15 minutes when they purchased the item. just make it available after 15 minutes. I dont know whether it conflict to the google policy.

120 Days. Not 15 minutes