Planet Fitness Outstanding amount harassment

2 Debt Collectors phoned me previously about my outstanding payments at Planet fitness after I cancelled my contract with them. I advised them that I went multiple times to the gym itself to cancel my contract after noticing that the debit orders are going off and I also advised them over the phone that I am not going to the gym anymore and my contract expired why am I still paying the debt orders and the debt collectors responded back to me and said that we can see that the contract expired and there is nothing planet fitness can do about it. On the contract it also states that they (Planet fitness) will let me know 40 days before hand that my contract expired which they never did. I also asked Planet fitness 6 times before to change my bank account details which, they never could do leading to unpaid debit orders on my other account witch I had to pay every moth for. Attorneys are phoning me know stating that this will become a court case and I will be blacklisted if I don't pay the outstanding amount. This is very unfair, and I am really not happy about this harassment.