Old Mutual fail to respond timeously

I have been employed by 22 clients to enquire about the whereabouts of their provident funds dating back to 1996. I have been in correspondence with the Old Mutual over the past ten months without reaching a conclusion. Since 1 December 2015, after pointing out that another one of the 22 clients had passed away, I have not heard a peep from Old Mutual despite requesting an update on 28 January 2016. How much longer and how many more people must pass away before a satisfactory outcome is achieved? As stated to the Old Mutual in my email dated 28 January 2016, I will have no alternative but to begin escalate the issue if a response is not received.