Hi afcjan,
If you look back at your bank statements from July last year to December when you cancelled the card, you will be able to see if payment was sent out to them.
If not, the best thing to do, as you have the goods and have'nt paid for them yet, is to contact them and tell them you will pay the amount, in full.
If it's a large amount, they may take it on installments, bearing in mind it was them that screwed up the payment when their computers went down, but at least, they wont threaten you anymore, as the next thing they COULD do, is refer it to Bailiffs and then you will incur more costs.
Best of luck to you.
yogi xx