Virgin Active demanding money when I dont owe them

Soon after the COVID-19 lockdown in South Africa in 2020, I called Virgin Active to cancel my contract around January 2021. While I don’t remember the exact date, the agent who assisted me advised me to wait until April, the month my contract would renew. She suggested that cancelling at that time would prevent me from incurring a penalty for cancelling before my contract expired.

In April 2021, I called again and cancelled my contract, and I also followed up with an email. However, by mid-2021, I started receiving notifications and calls claiming that I owed them money. I explained that I had cancelled my contract as directed by their agent, but they informed me that their system showed no record of my cancellation. I urged them to check the recorded calls for verification.

Unfortunately, no one followed up with me until this year, 2025, when I began receiving messages demanding payment for the outstanding balance. They are now using threatening tactics, claiming that this will ruin my credit score.

I need help with this situation because I am not prepared to pay the amount they say I owe.