Urgent Help needed

I've joined with a Contracting Company in Qatar last year now completing 1 year with them. From first itself they are not fulfilling the agreement, like though they offered me a family accomodation, from beginning what they provided was a shared bachelor accomodation & from the second month onwards the salary was delayed minimum by a month. Now my salary is pending for the last four months. And now, I received a better offer from another company & I asked my company to release me on completion of my first year and requested them for an NOC. Now, neither they are clearing my salary nor are they ready to provide me an NOC. Can anybody guide me here???