You're probably going to have to go a step further; something like Sift Science or MaxMind MinFraud along with automated SMS/voice verification of a unique phon

You're probably going to have to go a step further; something like Sift Science or MaxMind MinFraud along with automated SMS/voice verification of a unique phone number per trial. There isn't a carder in the world that wouldn't love to use a VPN service that offers free trials. They want the VPN to use as a proxy when testing stolen credit card numbers on other ecommerce sites... and they have plenty of cards to use to sign up for free trials with you first.