I know that their workload has probably increased immensely because of Brexit, but they seem to be getting all kinds of shit completely wrong.
I currently have an Amazon order sitting waiting for a customs charge to be paid even though I already paid Irish VAT when I bought it. Even if I wanted to pay the charge and get the thing I can't because they haven't sent me the details that I need to log in and pay. (Usually sent as a postcard if they don't have my email or phone number.)
A few months ago a friend sent baby clothes as a gift (about $50 worth), and they asked for €72 in charges and VAT even though children's clothes are zero VAT rated. I contacted customer services and they said my choice is to pay or not pay and have it sent back (I had it sent back). They couldn't have cared less that they got it wrong.
One of my friends had to pay charges on package from The Netherlands because it transited through the UK (not intentionally, the sender just put it in the post at her end and that's the route it took).
It's really frustrating, not least because there is no way at all of sorting it out. They can make mistakes/do whatever they want and there is no accountability.