Mental harassment at work.

Dear Sir, i am working in atul ltd. as a deputy manager. i joined this organization in december-2018. my GM is not giving work to me as per my job description (Job responsibility) and giving another department work to me. when i talked him that why he is not giving work to me as per my role than he told me that who are you to decide what should i give to you ? who is your boss? instead of giving correct answer such kind of excuses he told to me . i also told him that if you found that i did wrong work than give me point of improvement i am ready to improve myself.but he is also not saying any points and talking in general things but not giving me the proper reason for changing my role. (other person from the team is feeding his ear with wrong things and made my wrong impression in his mind.) so sir please help me to come out from this situation and how do i stop him to change my department. if you wants any clarification of situation you are free to contact me. please sir i need very urgent help... suraj makwana mo.[deleted]