I assumed you already have Amazon account when you bought Kindle Fire, but do you already have Audible account prior to it? If not and they asked you to sign up to Audible to get the free audiobooks, did Audible not send you an email when you sign up for it and before they start charging you for the next month? From what I know, they give one free audiobook upon signing up but then they charge you automatically the next, although they will email you first. I agree, though about using bitcoin for cases like this. If we used bitcoin, we would not have experienced autocharging into our accounts that websites and banks regulate.