I will explain in professional way:

Case i:
Your friend coming in another company and visa...within three months he can transfer to another company...but other company should have visa..and you should obtain NOC...but other company dont have visa...so you cannot do this..

Case ii
Your friend coming in another company and visa...he immediately issue Qatar Id...he cannot change company for 1 year....after 1 year he can transfer to other company............................