Lying and Cheating discovery medical aid

This year March 2020 my son and daughter was admitted to hospital and only to find that i was stuck with a 5139 blood test bill. Upon for the last 3 months trying to sort it out, eventually I found that Discovery does not cover the Pcr code 3974 blood test. Apparently they made it an exclusion in January of 2020. They did not inform me of changes and exclusions made to my medical aid and now j am stuck with a bill of 5139. Furthermore to contacting discovery thd consultant and team leader said that there is a new code that was give to ampath that could have been used. When I had asked them ghe code they said they didn't know the code. Upon contacting ampath I was told that there was no code given to them. I feel cheated because I feel discovery should be open and honest about changes and exclusions made to the medical aid. I also feel as a consumer I gave a right to know what changes and exclusions are made to my medical aid. Now I am stuck with a bill of 5139 because discovery felt I don't need to know about these changes.