1)Since you are on visit Visa you cannot work legally in qatar.

2) To work in qatar you must have valid work visa or else your company will get fine around Qr 50,000/-

3) Now what you do is politely tell your sponsor or manager orally that you don't like to work. if he is good he will give your passport.

4) If your sponsor is not accepting to return your passport then go to police and human right dept.

5) First tell your manager that you don't want to work.

6) No body can force you to work nor they can keep your passport legally.