Unauthorized subscriptions

I joined the gym in June 2018 and was told that after the contract end date, the subscription would go on month to month unless they don't receive payment then it will automatically be canceled. The gym fee went up and no one notified me. I gave my email address and 2cellpjone numbers but nothing.

Sometime last week I received an sms on my alternative number, letting me know that my acc has been handed over. I later received a call from a debt collector who told me I owe r950. Why? How? One of the VA agents told me I was supposed to go to gym and get my subscription canceled. Madness. Contract end date means I am not binded to anything after it? Why is there an unauthorized subscription after the end date because there are no funds? Who signed for this? I will not allow for my credit history to be affected because of their carelessness. Please remove me from the debt collection asap.