non payment of salary and reimbursement though having all valid docume

sir/mam, my friend was in service for last 3 months in a pvt company "Vedantu",as a sales executive.he always reached his target for sales and prevailed in his field. though he had an offer letter with all salary details, the company is not giving him a single penny after working til 12/1 am at night. can you please give me some suggestions about what next step should he take , to get what he deserve for his hard work ?