Complaint against landlady for harassment and torture

My parents stays in south kolkata in a rented room for last 40 yrs.Last year one of the son's of land lord reached out to my parents and informed that they would be constructing a building in the property.My parents gave them an no and were shifted to a different location.In the meantime the building was constructed but my parents are still out of their home.Initially it was agreed that that room would be handed to my parents within a year,but now it's more than a year and the house is still not prepared.When enquired about the situation they said that we have to build the toilets/kitchen at our own expence,even the cost of doors and windows were placed on our shoulder.To add further trouble they had stopped paying the shifting rent and it is being borne by my parents for last 2 month.Finally we decided to complete the house using our own masons/expenses .Now when the work is in progress they keep on causing hindrances every now and then.Is there any legal solution to this problem?