I was double debited my account and upon enquiring with them I was told that in the month of May their finance team made a mistake with my debited and nw they have picked that up so they are claiming the money back

I was double debited my account and upon enquiring with them I was told that in the month of May their finance team made a mistake with my debited and nw they have picked that up so they are claiming the money back. My argument was that I did not ask them to make that mistake on my account and why nw their negligent have to be on my cost ND further to that after finding their erro no one has e bothered to contact me to advise of their error and that thy are going to raise a double debit. The whole sga started with winning a reward I have wone a one month free subscription in the month of April so upon allocating my reward apparently their have allocated incorrectly nw I have to pay for their mistake. I emailed them and spoke to their consultant on numerous times but not get any Joy beside being told to pay the amount or else thy will block me