You can revoke a direct debit through your moey! app.
Find the transaction you want to revoke and click on it.
Go to the end of the transaction details and click on the |Revoke direct debit| button.
Confirm the action and that's it!
The option to revoke direct debits will only appear if it was charged to your moey! account and within 8 weeks after the initial debit on your account.