This is exactly why I refuse to purchase the paid version. I was just shown the tempting offer of the paid version at a discount. But I know how this works. Buy it now and end up having it auto-renew. I would purchase it if it weren't for this "feature" which is a scam.
I have the same headache with a magazine for which I bought a "one year trial" subscription. I've tried unsuccessfully to cancel my subscription but the auto renewal is conveniently done by someone they contract out to.
So, very the magazine claims they don't know who actually does the auto-bill. A magazine I really don't want anymore is now costing me $40/year.(Which would cost me $20/year if I were able to shop for the best price).