I have an approved H1B petition filed by a company (A) in US. I have not yet stamped the H1B visa. Now a company (B) in India with which I am working, will be filing a L1 visa for me. So the scenario is I have an approved H1B petition but I am coming to US with L1 visa and working for company B. Once I am there in US on L1 visa can I change to H1B after some days and join company A ? To change to H1B do I have to go out of US to get it stamped ? OR can the change over be done there in US itself ?