any "free offer - only pay the shipping" is like this. To stop monthly payments being taken from your account, in the very small print is a warning that unless you let the shipper know within 30 days that you do NOT want monthly shipments, they will continue billing you and taking money from your account.
It's not just Hydroderm - all offers like this will take your money. I know because I was taken - just once - and it took me six months and a lot of emailing, involving my bank, and arguing before I got my refund.
All that fuss and bother is a nuisance. So, if you want to order a product, do through Amazon - don't take advantage of these "free" offers from the product's site.
Product or Service Mentioned: Hydroderm Free Trial.
Reason of review: Problems with payment.