Viết lá thư bằng tiếng Anh phàn nàn về dịch vụ, nhân viên bưu điện

Dear X,

I'm writing this to complain about the attitude of the mailman today and the servie of your post office. I'm really upset now and I want to have a worthy compensation for what I have experienced. First, my sister sent me a parcel, and she decided to use the "Flash" delivery, which means the package will be at my house in less than 8 hours. However, the staff at the office made a mistake, he didn't select the "Flash" box, he tick the "Normal" one.  The delay of the parcel gave me a lot of trouble. A lot of my work has been put on hold to process information about parcels. And yet, the package was sent later than normal delivery. I do not understand why the post office is sending goods 2 days later than the scheduled date? In addition, the postman who gave me the package was very irritable, and even threw the package before I received it and signed it. When he got back, he even spilled a flower plant in my garden but didn't apologize. I hope I can get the right explanation and the right solution. My code is 3F7T88U, if you want to check for more information.

Sincerely,

Y