Paying of claims from MSA and not Oncology

I am a member of Discovery for 38 years now. Was never sick and hardly ever used my MSA. In 2020 I was diagnosed with stage 2 breast cancer and became a oncology patient. Problem is every time I go for visits or tests the claims with the C50.9 code on is paid to the service provider from my MSA and not my oncology benefit!!!! Every time I have to phone Discovery to do a claims adjustment, put the money back on my MSA and pay from my oncology benefit. Who is *********** or who does not understand what the C50.9 code means in the claims department of Discovery?