What are thr procedures for changing jobs from one company to another in Qatar?

A company brought me to Qatar under its sponsorship, i worked with him for 1 yr 8 months, i got another job and he gave me NOC to the new company. I signed a 1 yr contract with this new company, after which the contract was again renewed for another 1 yr, now i am in the 9th month of the 2nd yr contract, i just got another job, my contract says i have to give 1 month notification which i am ready to do, my concern is, is this company obliged to give me NOC as per Qatar Law since i did not exit the country before trasnferring to them? If they refuse, is there anything i can do? Since they did not bring me to Qatar, do they have provision under the law to cancel my visa? pls someone should help me. Thanks