Authorised Signatury

I am working in a MNC company in faridabad and I am handling taxation. during preparation I observe that same number sales invoice issue in two times. for example invoice no 112 dated 16april2018 sign by authorised person and same invoice no 112 dated 22july2018 sign by that person who is not authorized in GST registration certificate. I complained to my seniors but they did terminate me. am I wrong. please guide and advise me.