How do i evict people living in my house who have no lease or verbal agreement

HI I have an eviction question. I was leasing my house month to month on a verbal agreement with somebody named Sam. Sam without my permission subleased the property to 5 people and told them he was the owner. do those 5 peoples lease with sam have any legal value and do i have to go through a formal eviction process to get them out. Sam has not paid anything in 5 months and is not living in the house.