こちらの手違いでこのようなことになり申し訳ありません。
いまのお持ちの黒は返送のしてもらうので申し訳ないのでぜひ使って下さい。
白色の商品は出来るだけ早くあなたに送ります。
送ったらすぐに追跡番号をあなたにおくります。
それで発送させてもらってよろしいですか?
メッセージお待ちしています。
We are very sorry to trouble you because of our mistake.
We'd like you to keep the black one if you don't mind, since sending it back to us causes another trouble to you.
We'll send a white product as soon as we can.
Also we'll let you know its tracking number so that you can check when to get it.
we hope you would agree with this and let us move on for shipping.
We're looking forward to hearing back from you.
Thank you.