Is a company bound to pay ESI compensation and gratuity

My father died on 20jan2018. He was working in security guard private company.he was supervisor. Suddenly during duty hour in morning,he had paralysis,was referred to near by hospital.the hospital then referred him to sufderjung where he died in night. The company helped in pf and told they will help.we found that his ESI card was active after the incident and so the region manager is saying that we will not get benefits like pension and all but his proportion of ESI amount was already getting deducted.also company his not willing to give us gratuity. What we should do? Is it compulsory to give pvt.ltd. to give gratuity? What about ESI benefits? Please help!