If one of my products doesn't work out for you and you want your money back. Just let me know why you can't use it. I'll promptly refund your purchase price via whatever means you paid me (PayPal, check, etc.).
If possible, I'd first like an opportunity to fix it for you. Just contact me via eMail or telephone and let me know what the problem is. I'll make sure your problem goes away or return your money; your choice.