Suspicious activity by Virgin Active

I terminated my contract with virgin active and at the time of termination i had a pending credit with them. As per the discussions with their consultant they would charge me a pro-rata amount of R137 which to me doesn't make sense considering they owe me money. As per the agent, i forfeit the money owed to me due to gym closure as per Covid-19 regulations because Covid-19 is not Virgin Active's fault My arguement was that, Covid-19 isn't my fault either so why do I forfeit money owed to me by virgin active and still be charged upon membership termination. Further to that virgin active debited me an amount of R329 I doubt this is legal, how do you charge me 3x the amount you communicated, furthermore why do you insist on debiting me when you owe me money

From what i know is that gyms are entitled to charge pro rata upon membership termination but not when you're owing members money, moreso you've overcharged me on the prorata amount. That is not right and not sure that's legal