Some banks require the Direct Debit Mandate to accept the SEPA Direct Debit as a payment method. The mandate is generated when you book your plan with SEPA Direct Debit as your payment method. The mandate needs to be downloaded and handed in to your bank.
The mandate can be downloaded anytime in your account. To download it go to "My Account":
Under "Current Plan" you can download the "SEPA Direct Debit Mandate".
Here is an example of a "SEPA Direct Debit Mandate