Gems (Government Employees Medical Scheme)

My mother is with Gems for years. she did visit a dr. we had to pay the consultation fee cash and then claim it from Gems. The first time they did pay my mother immediately The second time they told us that the code that is used for the first consultation may not be the same, Gems will not pay out. The dr. told me that he uses only ONE consultation code. Now I must ask the dr. to motivate why he is using only one consultation code!! What can I do to get my mothers money out of GEMS???