over 3 years debt, i dont know off and never paid for and DMC is requesting payment

DMC has been claiming that i have an account that i am not even aware of, this account they have had it in their record for over 3 years to 4 years and only in 2020 they start calling me an claiming payment, this account has not had an interest in the past 4 years and they want me to pay and i dont even know what it is that i bought and i tried to follow up with Russells which is the store they claim i have the account with, also they dont have an oversight of this claim. They harrassing me and i cant pay an account which they have been quiet for so long about, I do have a russells account i am currently paying with DMC howver the one they claiming and requesting me to pay i refuse to pay it. also have logged a dispute with them for which i dont even think its on their records, my dispute is that i dont know of the account and i cant pay the debt which has been in existance for over 3 years without a payment (by law). i dont acknowledge this account. I have to explain this to every single person who calls me and no one ever follows up on my dispute. its a new thing everytime