I feel your pain. It is very, very, very much familiar to me.
It doesn't matter which carrier. They have about the same attitude on average, UPS, USPS, FedEx. They get a LOT of flack from people. All the time. People are not happy with them. Dogs bark at them and bite them. The gates are not open for them to deliver. Mailboxes are broken. Mail is not picked up and the box gets full. Etc. I don't think I've ever met a person who'd say "Hey, my postman is gr-r-reat!" They have learned to grow a thick skin, because otherwise it is too stressful, impossible to work there. It'd drive you nuts.
The problem with the thick skin - it is indiscriminatory to valid and less than valid cases, especially on ground zero. Higher up, you may find some more responsiveness.