CCJ over 6 years old with Link

[Guest]

Hi, I got a CCJ in 2010 for what I remember to be interest only on a bigger debt it was around the £300-£500 mark if I remember rightly I was told by the judge to pay £3 a month which has gone out of my bank ever since. The loan got passed on to Link in 2014 at which point they phoned me to give me new payment details and said I still had to pay the £3900 which was outstanding to which I said no I don't the CCJ is for £500 they then said they would take me to court for it for which I responded go on then. Now four years later after hearing nothing and still paying £3 a month they suddenly said they wanted updated financials to which I said no and by the way give me my account balance as I'm pretty sure its nearly fully paid after 8 years. They then sent a balance of £3600 I told them that's not my CCJ but they insist it is. I told them I have my CCJ in front of me and its not for anywhere near the thousands of pounds mark despite the fact I have no letters about it anymore. I told them to send me a copy of my CCJ for £3900 at which point they have told me they don't have a copy. I know for a fact my CCJ was only a few hundred as I appealed the CCJ in court and haggled the payment down to £3 with the judge.
My question is my CCJ is not on my credit file anymore and I can't remember the full amount of it and as I have no case number for the CCJ the courts can't seem to help me find it does anyone know where I stand with this as Link are adamant it is for £3900. If they can't prove it with a copy of the CCJ can I just cancel the payment and tell them I'm not interested as it doesnt seem there could be much they could do?

Thanks for any help