Standard Bank - They don't care about clients

I had +-R40 000 rand taken out of my mybiz account. As an overseas transaction. I informed Standard Bank immediately I saw it come off the account. From my track record they can see that my card is only used locally and only for small amounts. I am in possession of the card and have no idea how this transaction took place. Standard Bank immediately cancelled my card and said they were investigating. I have not been given any information despite phoning regularly and receiving a reference number. 6 months has now passed and no word from Standard Bank. I have phoned and they have promised 3 times to escalate the case and that someone would be in contact with me. I have still not been contacted. I have now lodged a complaint twice with the complaints department and am promised that someone will phone me or email me. To date still nothing. What do I do now? Who do I phone? I have been a client of Standard Bank for 40 years and never had such bad service.