A subscription can be cancelled manually or, when the agreement is cancelled all the subscriptions of that agreement are also cancelled.
Cancelled subscriptions are stopped, transactions already created can still be sent to the bank and a new subscription can be created from the cancelled one using the start over function.
Click on the subscription to open the details. Here you have a cancel button.

To quickly launch a new subscription based on a cancelled subscription you can click on it and use the Start over option. You then have the option to change any details of the subscription if needed or keep the current ones.
Click on Add to finish and a new subscription is created.

Transactions already created by the subscription can still be sent to the bank, edited or removed like any other open transactions. Future executions, if there are any, are disregarded since the subscription is stopped.