What's to be done when yoir own children cant be added in your medical aid

Im so disappointed by Bcima medical aid. I have children that i tried to add on this bcima as i am main member but bcima refuse due to the fact that these children dont share same surname with me. Bcima said they will only allow my children to be added on my medical aid when my name appears on my children's birth certificates. Im disappointed as i have to pay cash for my own kids at the Dr always as my medical aid cant help me. Im Jacob Bashipile MALESELA