Legally, can't they let the subscription run and say you owe them the money?

I can say you owe me money too. The hard part is collecting said money. The overheads of collecting from a non-cooperative customer would not make it worthwhile.

But what if they pass it to a debt agency? I think it's a risky strategy.

Ignore it? Even a debt agency has profit margins to hit and wouldn't take on unprofitable clients.

Depends if they allow signup from a prepaid visa. There's no one to chase, its a prepaid.

Managing subscriptions can be a pain, especially when you want to avoid endless emails. You might find using mailsAI helpful for organizing your outreach and keeping things tidy. It made tracking my subscriptions way easier without the hassle.

Tracking subscriptions isn't the problem. The problem is how much work it is to go and unsubscribe from many services. They all have a different process, that they don't make easy to find, and add as much friction as possible to discourage you. If you are trying to clean up your finances and unsubscribe from lots of things at once, it's exhausting. Having a single list of per-service cards that you can run down and click a button to pause or cancel is as much a convenience as it is a relief.

As a bonus, it's much easier to see where I've been spending so much money than running through my bank transactions and doing my own tally against their unhelpful categories and mismatched business names. And of course, the spending limits do as much to protect me from myself as it does surprise charges and price increases. It's been an invaluable tool for me, and I heartily recommend it.