Can somebody assist with advice on way forward in such a case

Hi my name is Ernest i have invested a good amount of money with RSA Retail Savings Bond/National Treasury,who are currently Ghosting my request for withdrawal during this Covid 19 related hard times.I have called then send emails then proceeded to their offices in Pretoria 240 cnr Madiba&Thabo Sehume to enquire what the problem was.My requests and attempts to get this office employees attention has been in vain for longer than 5 months.They have even informed their poor security officials to refuse access to anybody complaining or even making enquiries about Retail Bond withdrawals.