If you don't know a person's last name, use 'ma'am' or 'sir'.
如果你不知道一人的姓, 你应称呼他为 'ma'am' 或 'sir' 。
Thank you for your inquiry, but we cannot make you an offer right now because we are presently unable to obtain appropriate materials.
谢谢贵方询价,但我们不能马上发盘,因为目前我们得不到合适的原料。