If you are on Business Visit Visa and wish to transfer to Work Visa to another Comapany then NOC is needed.

But if you go back to your Country and Comeback on the new Visa NOC is not needed.

All business visit visa providers advise you to exit and come in new visa so that they donot loose a Visa. But if you pay QR 500/- to them thay may accept as it is only visit visa NOC