用英语「处理客户投诉」
I've been waiting three weeks for my order and nobody has given me any explanation. Can you tell me what's actually going on with my shipment?
I completely understand your frustration, and I sincerely apologize for the delay. Let me pull up your order right now and find out exactly where it is.
I've heard that before and nothing ever changes. How can you guarantee that this won't happen again with my next order?