BAD GYM

So I had a 24-month contract, paid the full 24 months, then wanted to cancel my contract, I was told to go into the branch and cancel my contract, which I did, then the monthly debit order still went off for a few months, I then phone and the manager at the time was extremely rude to me, I then cancelled the debit order at my bank, only to get a phone call today saying that they are going to blacklist me..... I told them if your house is not in order, don't threaten me.