Zone Fitness Lenasia - Trying to ****** money from people after they have paid their contract in full.

I had a 2 year contract with Zone Fitness Lenasia, I took this contract out in March 2018 and it concluded in February/March 2020. I paid diligently every month via debit order for the duration of my contract. I sent a cancellation email during lockdown to Zonefitness notifying them that my contract has ended and I do not wish to continue. However they insist on telling that I am in arrears and send me messages telling me to pay my arrears even after sending emails upon emails telling them that I have paid my contract in full. They have done this and are doing this to so many people, who will hold them accountable for trying to ****** money from us? good people who have paid for 2 years and have paid that contract in full. ZONE FITNESS LENASIA NEEDS TO BE SHUT DOWN, what they are doing to people is not right, just go on to facebook and you will see the comments from so many people complaining about the same thing.