This is actually a widespread practice among German ISPs. I once fell for this myself. What they do is that when you order something they automatically add some service most customers almost certainly don't want or need (like a software package or homepage webspace) and that is free for the first months. You cannot remove that from your order, you have to later cancel it manually. As it's free at the beginning new customers checking their bill won't notice it as something odd (it's some free addon, why care?). Then after some time it starts costing a fee.