我們變更了我們30年前到現在的付款條件 只因為我們要配合貴公司的要求 我們提出一個買家客戶最基本的請求想了解出貨日期. 你們這星期四可以收到訂金, 難道不能先針對星期四後的 船期確認嗎? 請英文高手可以幫我翻譯成英文嗎? 請不要用翻譯機.謝謝!?

We have changed our payment policy which lasts for 30 years because we want to match with your requirements. Based on the basic customer's demand, we need to know the shipping date.  You will have received our down payment by this Thursday. If possible, please notify us of the shipping date. Your cooperation is deeply appreciated.

恕不能完全直譯! 明白了你的處境後,我用了我的語調寫了英文版,態度有交涉味兒.
To accommodate your request (/To satisfy your requirement), we have even compromised our payment policy that has been adopted for 30 years. 
It is every buyer's basic request that we have made for the information of the shipping date. 
As you are going to receive our deposit on this Thursday, I can hardly imagine that it is impossible for you to confirm the date based on the ship sailing schedule after Thursday.
Please cope.