You may only change sponsorship after you have been with your present company for a period of two years. However, you may do a six month release if both companies are in agreement. A transfer of sponsorship does not require a NOC, what you do require is a signed Transfer of Sponsorship form and a Police Clearance Certificate. A NOC is only required if you leave the country and have your RP cancelled. A NOC will enable you to re-enter Qatar and find employement with another company.