Best answer by woz
easily sorted, go to help in app or online logged in, ask wattbot, type "message the team" and ask for a part refund/direct debit review as your payments may be set too high depending on what your normal monthy payment is. Replies within 24 hrs.
Also might be an idea to submit some readings if you haven't already done so.
Don't forget you should be in credit by around a months average payment when you've paid your DD. (So you should subtract that from the £500)
I'm in credit for over £500. How will this be refunded to me?