Policy withdrawal

I am unable to make a withdrawal from my old mutual investment because the consultant who helped me open it used my father's surname instead of my mother's surname (which is on my ID).

I realised the wrong surname upon the initiation of the policy and immediately contacted the consultant to notify him of the mistake, he said he'd fix the problem but instead he added the ID surname on the policy leaving me with 2 surnames on the policy.

Now the issue is that they keep on saying I must provide proof of surname change in terms of a marriage certificate. I provided my ID copy, banking statement and an affidavit stating I have never been married and that the mistake was made by their consultant. I have not received communication as yet and I'm serious need of the money, what do I do in this regard?