Cancelling of a subscription payment, without simultaneously notifying eg continuation (such as through an alternate payment means), is a clear and unequivocal indication of termination of the agreement for which the payment was being made.
A company has a simple avenue to avoid inadvertent cancellation, they just ask the customer "did you mean to cancel, please contact us by $date to continue your subscription".
But that's preferring the citizen over business interests.
If it is easy to cancel then you should cancel. However if it is hard have your credit card cancel for you. (not all will, but some will) The advantage is they work for you and can put pressure on merchants to make it easy so they don't have to be the middleman.
A company has a simple avenue to avoid inadvertent cancellation, they just ask the customer "did you mean to cancel, please contact us by $date to continue your subscription".
But that's preferring the citizen over business interests.