So sorry to hear this celcat. Not sure I can offer much advice.
I have had a store card clonned a few years ago and then last year I had a couple of credit cards with payee not present type payments taken from them (phone top-ups etc to the tune of about 400 quid Grrr! on two different cards).
I thought it might be an inside job call center staff as I had 4 credit cards at the time but the 2 that were subject to the fraud were with the same organisation. One had been cancelled by phone six months before, cut up & destroyed by me & all statements shreded.
so how that wasn't an inside job I don't know. Tesco credit card, I forget what bank underwrites Tesco.
Needless to say Tesco were aghast when I suggested it might be an inside job.
but unless someone crawled in my bin and reconstructed the card I don't see who else could have had the details that far down the line I had only used it once to buy an MFI kitchen about 2 years before.
I never cancel by phone now always in writing and ask for a written acknowledgement of cancellation. Which suspiciously you sometimes have to chase.
From what I read some banks are better at sorting these things out more quickly than others, but these cases all do seem to get sorted out in the end. Don't know if thats any consollation ? But a horrid thing to happen to you. Hope it gets sorted speedily.