Last in is what usually applies. So if the H-1B COS from L-1B to H-1B was applied the latest than that means that the L-1B ought to be denied later since you already have your H-1B now which was filed after the L-1B extension with employer A. So you can stay with employer B on your H-1B.
No offense, but, by filing multiple applications, you have made a bit of a 'mess' of things.
Talk to the immigration lawyer working for the company you want to work for .... be completely honest and have him/her sort things out.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.
I agree with Mr. Capriotti
Samuel Ouya Maina, Esq. 415.391.6612 firstname.lastname@example.org Law Offices of S. Ouya Maina, PC 332 Pine Street, Suite 707 San Francisco, CA 94104