Happened twice now - both with tescos…curve declines the transcation to the supplier, but the underlying card is charged anyway!
First is finally resolved but the second is stuck with support who dont even read the messages properly (how does declined look like pending!) and reply with boilerplate messages and support links.
As for trying to get an explanation - would currently just settle for my money refunded!
There really is no excuse now for the years of appalling customer service on what should be such an excellent product.