You will no longer be able to charge the consumer’s bank account or credit card with this mandate and all connected subscriptions will be canceled.
https://docs.mollie.com/reference/v2/mandates-api/revoke-mandate
function(string $customer_id, string $mandate_id, array $params = [])
{
$customer = $this->getCustomerFromId($customer_id, $params);
$mandate = $customer->getMandate($mandate_id);
$mandate->revoke();
}