We strongly recommend that this method is cost-effective.
我们强烈推荐这种高成本效益的方法。
We deeply regret that we did not meet the deadline.
未能按期完成，我们深表遗憾。
We totally reject your final offer.
我们完全不接受你们的最终报价。
We fully admit that our service is not to your satisfaction.
我们完全承认我们的服务没能让您满意。
We sincerely hope that you have enjoyed our services.
我们真心希望您满意我们的服务。
We categorically deny your accusations.
我们坚决否认你们的指控。