Trinergy threatening to Blacklist me with ITC due to their mistakes.

I signed up for a contract at Trinergy early 2023. I subsequently left the gym a year later and sent a cancellation request, as well as for them to provide any penalty fees. I received nothing. I called multiple times and still got no feedback. All the while I was still being debited the monthly membership fee. A few months later I stopped the payment with my bank as I had not used the gym in months and was still paying for it. I then received a call and an email for cancellation fees which I declined to pay as I cancelled and already paid many months worth of an unused membership. I have now been called by debt collectors and they are threatening to blacklist me on ITC as Trinergy has handed me over for non-payment on my account. I am being punished for the unprofessional behaviour and uselessness of Trinergy themselves. This is unacceptable and I will fight this.