Ruby Hospital — Cghs rate charges more than fixed rate

My parents is working in coal india they went for a treatment in ruby hospital opd. They fall under cghs scheme provided by coal india.But this time they charged around 850rs. As per as the government cghs charges by the government is 350rs.This is clearing cheating my hospital management I want my refund of 500rs which I have paid extra in the hospital bill was Done on my mobile no [protected].