Executors of late estate showing a conflict of interest

My father passed away on 17 March 2014 after a brief illness. In his will he had named Old Mutual as the executors of his estate. Old Mutual went on to nominate a company called Sentinel Trust International to handle the estate. To date all we have gotten from Sentinel Trust International are threats to auction off immovable property in order to cover the shortfall in the LND account. They have not gone through even a single avenue to assist us in recouping funds from my father's various investments, as such those debts have since prescribed. Now they are unwilling to plead prescription on our behalf as well since that will affect the 3.5% that they are entitled to once the estate has been devolved. Most disheartening is Old Mutual's attempt at robbing us of the 2/3 remainder of our father's retirement annuity. In the 4 years since his passing we have not received even a cent of this money. The financial advisor who was in charge of this fund, a Mr. Igne Campher, suddenly informed us (after submitting beneficiary forms) that we are not entitled to that money. Citing that my father had not signed a nomination form. This is in direct contravention of section 37c of the pension funds and retirement annuities act but when we try to follow up on this we get ignored.

We have tried many other ways of addressing this matter and now all we want is a letter of renunciation of executorship for Estate Late ET Memela so that we can finalise this chapter of our lives and let our father's spirit rest in peace.