Mullvad uses the superior way of not having a real account at all - you just get a number you can "deposit" money into.
It's the only way they can reliably prevent abuse like a thousand people using one number - because this way you can just track the number of open connections per account number.
This is superior to tracking IP-addresses to detect fraud for obvious privacy reasons. I do a similar thing for a service I run.
Out of curiosity, how do you even manage to use more than five devices for private use at once? Even just owning that many is unlikely.
It's the only way they can reliably prevent abuse like a thousand people using one number - because this way you can just track the number of open connections per account number.
This is superior to tracking IP-addresses to detect fraud for obvious privacy reasons. I do a similar thing for a service I run.
Out of curiosity, how do you even manage to use more than five devices for private use at once? Even just owning that many is unlikely.