I was really surprised to find that my attempted transaction using my credit card to Argos was blocked today as a +90% chance of being a scam!! I wouldn’t have thought that a company with Argos’ reputation would be scoring as a scammer. Any idea why this would have been?
I decided not to appeal the block as I didn’t need the hassle.
False positives can happen, best to report it and someone will be able to take a look
Fraudsters will use stolen debit cards to pay down debt/bills - seen it many times in a previous job.
I once tried to use Monzo to pay for Apple Care and it was blocked for a scam. 
Argos seemingly had a breach a few months ago so could be related to that. No official statement but a lot of anecdotal evidence e.g. https://reddit.com/r/Argos/comments/1ojf5sl/account_hacked/ and https://www.emcrc.co.uk/post/currys-and-argos-account-warning-issued-by-police
I recall some data being shared previously suggesting that the Apple Store is one of the most common places where stolen cards are used for purchases.
Seems likely, but my attempted purchase was online.
It really is bizarre how much fraud happens there.