GoCardless - Create Mandate Outside of WHMCS

[thisismatt]

Hello all

So it's possible for a client to create their mandate outside of WHMCS, using the GoCardless site itself (you get the link from from clicking 'Add new, customer' within your Dashboard). But, how would I link that new mandate to a customer in WHMCS to ensure that their invoices use that Direct Debit? In fact, is it actually possible to do this?

Thanks!