eBuyer.com - goods not received

[shopper150]

I purchased around £800 of goods from eBuyer.com and paid extra for next day delivery.
The goods did not arrive on the specified day, so I waited a couple of days longer and still did not receive them. The tracking number stated on their website was invalid.
I sent an enote via their website to chase the order and ask for the delivery charge to be refunded.
They did not reply for a couple of days, so I chased again and also mentioned that the tracking number doesn't work.
They eventually replied and said they would look into it and come back to me.
After chasing a few more times, they send me a Yodel proof of delivery with an unrecognised signature.
They stated there is nothing more they can do.
I have asked for a refund a few more times but they are refusing.

I paid using a business visa debit card.

Can anyone advise what I should do? Would my card company refund me?
The interesting this is that I have checked my previous orders (which are all recent) and all the tracking numbers on their site are invalid.