Most horrific experience- service to cry about.

Package of a book stuck at customs. First, it wasn’t released as it was “a business package”, although, which according to them, I needed to have a business registration number - which is not a legal obligation for a sole mandate. My name is also on the invoice, not just the practice name… When explained this, they requested an invoice from the supplier- stating they need a commercial invoice? After this, I was advised to send the original invoice to verify my name. They then taxed me on the amount for the online course I attended - the only invoice I had (which includes the price of the book that needed delivering) and not just the book. I phoned to verify the cost of the package, which they confirmed, but taxed me almost 3x the price of the delivery. After numerous emails and phone calls, they sent the correct amount to be payed, but 2 hours later, I received emails again, stating I need to pay the absurd wrong amount. They then went as far as sending to the supplier that I’m not compliant in paying this huge amount, after I spent forever on the phone - attempting to rectify the situation. I’m honestly speechless with the horrific experience. The supplier is in Canada, which complicates the very unnecessary back and forth. I’ve been receiving almost 5 emails a day demanding payment, but no attempt to assist with rectifying the error😂 It instils feelings of hopelessness and despair. DHL Express - Excellence. Simply delivered??