UIF Claim - non-payment since June 2020

I am now trying since June 2020 to get payment for unemployment. They can't attend to their claims, but forwarded me a letter last month that I owe them R6,000 since 2007. First time I am informed of this. Why can't they just deduct, if it is valid, from the money they owe me? Don't try the helpdesk. It is just dropped calls, poor telephone reception and poor service. What must a person do to get what ia owed to them?