Fast Track Reclaim PPI saying they acted as agent for my HMRC Tax affairs HELP!

[Vixated]

I used Fast Track Reclaim in 2019 for a PPI claim. I received a refund from one of my credit cards for PPI and paid Fast Track Reclaim's fee. I thought that was the end of my involvement with Fast Track Reclaim. Fast forward to 2024 and I received a P800 letter from HMRC informing me of a refund and they paid directly into my bank account. A few days later I received an email from Fast Track Reclaim demanding a fee for having sorted out my HMRC PAYE refund. I refused to pay their fee as I did not authorize Fast Track Reclaim to act as my agent for my HMRC tax affairs. I was totally UNAWARE FTR WERE ACTING AS MY HMRC TAX AFFAIRS AGENT. FTR emailed me a copy of their Terms & Conditions showing no signature together with two emails they allegedly sent headed up as PPI Reclaim. I only signed up to Fast Track Reclaim for a PPI claim. I have requested copies of the Deed of Assignment Fast Track Reclaim say I signed and other documentation, but they have ignored my request. I have also written to HMRC requesting copies of all documentation sent to them by Fast Track Reclaim., but no reply yet. Following a telephone call with HMRC they have sent me a letter confirming that Fast Track Reclaim have now been removed as my agent. I need advice about whether or not I should pay the large fee Fast Track Reclaim are demanding? I contacted Action Fraud who advised me not to pay, but I am worried I will end up having to pay legal fees, interest and a County Court Judgment. PLEASE can anyone advise or help me with this?