Well Salam International are a big well known company, however before joining i advice you to get from them a written paper that if you are not satisfied and you want to leave they will issue a NOC ( no objection letter) that will give you the possibility to work with other company in Doha.
Without this paper you can not work in Doha.
They will tell you they are a well known company and listed in Doha stock market, and their HR will tell you a lot of nice stories, however do not accept without this paper.