Update banking details

I have recently changed my banking details and need to update them for my Sanlam Shares. I called the number given (in bold numbers) on the shares form (***), only to be told that this number is not available to call. I then found a number for Sanlam and got through but I was told that I had to try another number ***) This number says that they are not available to take my call now, so if I want to, I can leave a message- I tried this number a few times. There is no other means of contact given. Please can someone give me a number that works where I can update my details - this should be a simple procedure!! And not a run around. Tomorrow I may forget to try call again and will lose out.