Pension fund short payed.....

Old mutual short pay me my pension fund. Old mutual was suppose to pay me R24 918.57 from R39 127.46 but I only received R4 500. 00 and when I enquire they claim that all the fund were took by Sars (R20 418.56). I have call, sent emails and even went to the office. Without any help Never invest nor have pension funds with OLD MUTUAL IA THE WORST BANK/FINANCIAL INSTITUTIONS EVER!!!!!