Making people ask permission to leave is a good way to make sure they never come back. So they can do it themselves.
From their own dashboard
A subscriber can cancel from their account on your website. They do not have to email you, and you do not have to lift a finger.
This is deliberate. A cancellation that takes one click leaves someone with a decent impression of you, and people who leave with a decent impression sometimes come back. People who had to fight their way out do not, and they tell others.
What cancelling does
Future payments stop. Nothing more is collected.
Past payments stay. Cancelling does not refund anything, and it is not meant to.
Access continues until the end of the period they have paid for. They keep what they bought. If they cancel a month in on a yearly package, they keep it for the remaining eleven months.
That is fair, it is what they expect, and it means a cancellation is not an emergency.
Cancelling on their behalf
If a customer asks you to do it, you can.
Go to Mollie Payments, then Transactions. Find their payment, open it, and cancel the recurring subscription.
Cancelling as part of a refund
This is the case people get wrong, so it is worth being blunt.
If an unhappy customer asks for their money back, and you refund them but do not cancel their subscription, they will be charged again next month. You will then refund them again, and by that point they will be genuinely furious, and quite right too.
When you process the refund, tick Cancel the recurring Mollie subscription (no future payments).
The plugin offers it in the refund screen precisely because this mistake is so easy to make.
Winning them back
A cancellation is not always final, and the moment of cancelling is not the moment to argue.
But an expiry warning email, sent to someone whose access is about to end, sometimes brings them back. That is not a trick. It is a reminder, sent to someone who once thought you were worth paying for.