Gym company is trash

My contract with Gym company ended in February and only in May I realised. When I phoned to officially cancel, they told me I owed 2 months fee that bounced which is R500. These ********** have been debiting 200 from March to May =R600 but refusing to cancel because, according to them, I still need to pay the R500 I owe. I am still paying even now cause.*****!!!!