I'm glad this is working for you. When I tried (a few years ago), UPS refused to send the commercial invoice and bounced me around from person to person on the phone, all of whom seemed to have no idea what I was asking for. My partner tried and had the same experience. I think we tried about 5 different times and got nowhere.

For us, they had delivered the boxes while we weren't home and then sent the bills later and then to collections (their own private collections company as it turns out). We sent a demand letter to them requesting proof that we accepted the delivery (we obviously hadn't), and ultimately never heard another word from them. Collections letters and phone calls stopped. Not saying this will work for everyone, but we were relieved as we didn't actually owe any duty (we were shipping our own stuff) and tried so hard to complete the process the right way.