VERY VERY BAD SERVICE FROM DISCOVERY MEDICAL AID

I have been paying a amount of R988.00 . per month for my medical aid, I recently cancelled my medical aid in April and had already saved more than R12000, I joined another medical aid scheme that is cheaper, i now need medical covers discovery says u money is not mine its for the scheme i am not able to use it for any hospital expenses, The question is that because i contributed that money for medical expenses why cant i use that money for that instead it goes to the scheme while it was paid from my salary, Discovery medical aid schemes you are ripping us our money that we worked so hard for.