If your in laws made you marry their son on some lies and made end number of promises because of which you agreed to get married in the first place . In detail suppose you told them that you want to continue your further studies first then would want to get married but they promised you they will never waste your time and will make you do your studies infact they tell you that is the reason they want you to get married so they can make you study and post marriage they tell you on the face that was a lie and they got you married so can work for them and many things like these .
What should we do ?

You cannot break this marriage just for that.
They committed a great sin by lying. You are not obligated to work for them. You can continue your studies