Discovery abuses its clients

I am so annoyed. I paid cash at the doctor, then submitted my claim. Discovery rejected it without reason. I called them, using MY airtime, only to be told that this was because the doctor entered the incorrect ICD10 code. Firstly, I am not a medical professional, so how in the world am I supposed to know whether or not the code was entered correctly. Secondly, what is so difficult with discovery actually CALLING its clients who pay them exorbitant amounts of money each month to ask for additional information? Thirdly, what measures are you as discovery putting in place to ensure that doctors are forced to put correct information? This is not the first time I have complained about this, so you are clearly not taking this seriously. Why are you abusing your clients?