So there's no subscription thing going on, you just manually pay invoices?

I once spent an entire year issuing chargebacks on AWS charges coming from god knows what AWS account. Most likely some client project I forgot about and didn't have the login to anymore, who knows. Makes me think about that - for a service where you can't login if you lose the credentials, how do you cancel a subscription? In my case I had to eventually just cancel the credit card and get a new number.

No subscription. It’s pay as you go. You top up $X and you get X months. That’s it. If your month expires, it expires. Just top off and you’re good to go.