Atrocious export department

My customer, a large art gallery in the United States, requested that I send their order via their UPS account. I delivered the parcel last Friday, March 4th to the depot, and asked the customer service agent to make sure the paperwork was in order. Five days later, I looked up the tracking number and saw that it had not left the country. I called to find out why, and was told they would phone me back straight away. Around 5 hours later I called them back and was told there was a minor problem with the invoice. I fixed it and sent a new one by email immediately. Two days later the parcel was returned to me with no warning, and no one was able to tell me what the problem was with the paperwork. The next day the parcel was collected again. Today, Friday, I received an email at 4pm asking me to get a form from my bank, which was required when parcels were over a certain value. They have known the value of the parcel since I delivered it to them, but this is the first time they have mentioned this form. Due to their ineptitude, my parcel will arrive after the cancel date for the order, and, if they still accept the parcel, I will be paid 12 days later than I ought to have been.