私は貴方のメッセージの返信として、全額返金を求めるメッセージを送りましたが、貴方からの返事がありません。
返事がなければ、この問題をクレームにします。
早急に返事を下さい。
I sent you a message as a reply to your email saying that I wished to claim the full refund from you. However, I have not heard from you yet.
If you do not reply to me, I will lodge a complaint against you.
Please reply to me as soon as possible.