Please help

I have a flat in Jhb, I bought the flat with a tenant staying inside the apartment, I signed a lease agreement with a tenant for 12 months which ended on the 31 of July, The tenant did not pay any security deposit, He failed to uphold the contracts from last year, now since February He did not pay not even for water and electricity, Now he vacated the apartment on the 15 July 2020 owing the amount of +- 25000. Please help me, how do i get him to pay the money.

Thank you