Mulvad gives you a 16 digit random number when you sign up. Anyone with that number can use that account, it's on you to not lose it, if you do you have to make a new account. You send them money and an account number and they add balance to that account. When it's out, that account is blocked from service until they get more money. You hack their service and you get a list of numbers and whether or not they have service. They keep no documentation and if you pay with card you have to manually input every time. I know them better than they know their users.