Gems refuses to pay

After adding my parents on my medical aid i was told that certain illnesses will not be treated until they reach a waiting period of 12 months.. Ohk i understood that. I had to negotiate them to cover my dad for parkenson's diseas since he did not have the disease before joining the medical aid.. That was then sorted.. Now the medical aid went and collected my dad's clinical information hence he was a member of gems before.. Joining under my mother's name who has since retired.. Now gems is restricting prostate on my dad because it appears that he once checked his prostate while on my mom's medical aid.. Now what i neesd to know is.. Why are the restricting any treatment on his prostate because when he was checkes years back there were no medical issue with the prostate.. Doctors checked it because of his age and stating that men his age should do these check ups.. He was never disgnosed with cancer.. They just checked.. Right now he is hospitalised and doctors want to check the prostate but tjere are restrictions.. Yet we pay thousands for medical aid.. Then they always try to play mind games with our heads! I would understand if he had cancer disgnosed back then before rejoining under my name