Hi derekzhu922,
This isn't good to hear at all!
It's likely that your manual payment made on 18/1 hadn't reached our system by 21/1 resulting in the direct debit being taken as scheduled. For future reference, we encourage customers with a direct debit arrangement to process any manual payments at a minimum of three business days before their direct debit date.
In the meantime, you can have this second payment refunded back to you. You'll just need to get in touch with our web chat team here to arrange this!
Kind regards,
Jayden