Dispute against planet fitn

My name is Lesego Veronica Segosapelo. I joined planet fitness on the 27th April 2016. I s8gned a 24 month contract, Everything was ok until October 2019 when I saw that they have debited my account. I then went to the bank and reversed it because I knew that they made a mistake. My contract with plant fitness was for 24 month. After the completion of contract I then asked them to end it through their call centre, the consultant that I spoke to adviced me to freeze it instead of ending it. He also told me that they won't charge me anything until I decide to unfreeze or renew the contract of which I agreed on. Then the following month they did not charge me and I was happy because they honoured their word. I was suprised to get a message from Ludau Attorneys stating that I owe plant fitness about 1500 that I know nothing about. Now I am getting this messages from them regularly. I also called planet fitness to enquire about this debt but they just told me I am still a member and I owe them. I really don't know what to do. Please help. The last payment that I owed was 2239.24 rand which I paid in 2018. I haven't been there ever since.