Tracing Post Bank head office.

Can some one help me to locate the Post Bank offices or Head Office,many SA Post Office employees keep refering us to google for the tall free number and no one answers on the other end.Its either the answering machine will say you are number 14,then 5 minutes later you are number 20 then the phone cuts off.We have invested a lot of money with the post bank yet they can't be traced.