[boring_twenties]

No idea about Revolut, but Citi has had a similar built-in feature since something like 2005. It's called "Virtual Account Numbers." You can set total spend limits as well as expiration dates. Once either one is hit, transactions will simply be declined.

[nybble41]

As others have mentioned, that prevents the bills from being paid but it doesn't nullify them. They can send the unpaid bills to collections, which creates more hassle for you and negatively impacts your credit score. I wouldn't recommend relying on virtual accounts and spending limits as an alternative to proper cancellation.

Blocking the payments can still be a good idea—money you have in hand is worth far more than the dubious hope of a refund—but you should also keep clear documentation showing that you cancelled your subscription following the specific steps required by the contract before stopping payments.