human rights for this situation?

Hello everyone. I want to ask for help. I have a friend who's now working more than 2 years in Qatar, he is working before in a new established company and his main sponsor is the sponsor of the company. His sponsor owns a lot of companies and as per Qatari law he can work to other company for as long as it has the same sponsor. Am I correct? Now, the company has been already closed and his manager promised to give him a release and NOC. For 3 months he is struggling to find a new job. Last week he was able to get a good job that offers a salary more than he could ask for. When he ask for his NOC and transfer of sponsorship, the main sponsor doesn't want to give him, even the fact that his previous manager is willing to give him the release. Now, the sponsor is not allowing him to work for another company and they wont even give the salary that he used to have. The fact also that he didnt work for them at all and they are forcing him not to work for others. Who can we ask help for this kind of situation? We need some serious advise... Thank you.