No response to emails

I have been sending emails to Discovery Health to change the dependent to the main member and vice versa. The first email was in July where I received feedback from Discovery requesting me to complete the continuation form. I did and sent the form along with all the docs back. I never received any feedback. I do not have a reference number because I rep**** to a previous correspondence with Discovery. In August I have sent rumerous emails requesting the change. When I called the call centre , they simply say that they never received my emails. How can 5 emails disappear. I then emailed the whole discovery group hoping that my request can be amended to. But still nothing. Please help me with updating the main member on my medical aid.