I see your point of view and @clifford3470 hasn't elaborated if they plugged in flat rate shipping or calculated shipping.
All he said was "I have sold a item to a overseas buyer in guernsy , the delivery quote was 3.50 ,but true cost is 45.oo what should i tell the buyer,obviously i cannot afford to honour the contract"
If they used calculated shipping and put in accurate weight and measurements, then there is an issue somewhere with the postal service or shipping company's quote. BUT if they determined what the shipping cost was, and put that in, or didn't bother with accurate weight or measurements, it's on them, but it sounds like they made a statement that they weren't shipping it anyway, so I don't quite know why they posted on here.. I don't even see anything in their sold or completed filters any way...
