Ok now that is a different story, after reading their emails for 10 times or so I think what I understood from this part:
... we will deduct the APW7 price with new order, and this amount difference will be transfered to you Bitmain balance account which can be used in future orders.
Is that you will need to re-order the miner without a PSU through the single-use link they sent you, which is a special link to a miner only, and they want you to choose USD wire so that the order won't expire until they mark it "paid", they will probably deduct the mount from the first paid order and send it to fund the "new" order, and the balance will be sent to your account.
So it looks like you need to email them again and get another link, it's really hard to understand Bitmain staff, I guess we all suffer from this.
A tip: Always email them in the morning (China time) you will get a much faster response.