Obviously there is no point using a VPN if they know who you are to begin with. If you aren't going to trust the rest of the internet to know your identity and your habits, there is little reason to trust a VPN either.

The solution is to use a VPN that accepts cash payments and uses numbered accounts. To my knowledge, the only one that does so is Mullvad, which is based on Gothenburg, Sweden. The way you use it is that you create an account on their website, which has about a 15-digit account number. There is no password. You take some cash and put it in an envelope and mail it to Gothenburg, Sweden, and put down Mickey Mouse or whoever you want on the return address of the envelope. On the inside you put a note saying what your account number is. They count how much time the included cash buys you and credits that to the account number you tell them. They have no idea who you are. Their software works on all major operating systems and tells you how much time you have left on your account, and they have servers in all major cities.

Oh, and they accept all forms of currency. You can mail American cash dollars to Sweden and they'll just calculate the exchange rate and credit your account.

No need to trust them to keep you secret. All you are to them is a 15-digit number and an envelope with a $50 bill in it from "Mickey Mouse".

There is no other VPN I know of that is set up this way. Their rates are reasonable and competitive, the speeds are good, and they allow up to 5 devices per paid subscription.