Canceled account sent to debts collectors

I cancel my membership in Feb 2020 paid all fees (40% of remaining ) South Africa went to lock down u continued to debit my money from the bank even though I paid all cancelation. Now they handed over my account to debt collectors saying I own them R7000 went to the gym receptionist was rude didn't even want to look at my receipt and said I must speak to debt collectors.why I must speak to debt collectors whn I pay fit24gym all cancelation costs.