Hi Tim, JC International certainly is a legit company but it is based in the US since 2002 and trades in the UK under the name Creditlink Account Recovery Solutions (CARS). They are also FCA regulated according to this review on google: [https://moneynerd.co.uk/jc-internationa ... ollection/
I believe they mainly purchase debts from telecommunications service providers, utility suppliers and other debt collector businesses so I’m not sure about Barclays.
There’s still a chance you might be being scammed by someone framing themselves as JC so the best way to check is to contact your creditor who the debt collector purchased the debt from (you should have received notice of this) and to ask JC for proof of debt - there is some guidance on how to do this in the aforementioned blog post.
If it comes down to it and you have debt collectors on your doorstep (again you should have received notice of this 13 days before they turn up) always ask for ID and license. You don’t even have to open the door, just talk through the letter box and ask them to hand it to you that way.
But chances are, if you think you may have a debt with this company, then the debt is likely real and JC are legitimately chasing you. Just send a prove-it letter to be sure or check your credit report for late/missed payments with barclays.