Is testgorilla.com Safe?

TestGorilla took money from my credit card for a service that I don't want. They refuse to reverse the payment. I signed up for their service on a pay-as-you-go basis. They converted this into a pay-annually-forever-unless-cancelled account. I used their services a year ago, and haven't used them since. Out of the blue, and without any warning, they took $650 from my credit card. They claim to have sent an email 3 months ago, warning that if I didn't cancel, they would bill me. I did not receive any such email and have confirmed this with my ISP. They are charging me for the next 12 months. I've told them clearly I don't want to use their service for the next 12 months, and they should reverse the payment. They refuse. They claim that by signing up originally I somehow agreed to this pay forever scheme. The reality is that at the time I signed up, I was in email communication with them, and told them I used wanted to use their services for that one month. They explained that I had to pay for a year on a pay-as-you-go contract. I paid for that year. I used them for that month, and never since.