if you changed status in the u.s. from b1/ b2 to L1A which it appears to be the case, your b1/b2 is effectively canceled. you cannot maintain 2 visas at the same time. if you did change status here in the u.s. to L1A after entering on b1/b2 and you exit the u.s. you must go to the consulate for visa stamping so that the new L1A is in your passport before you will be allowed to re-enter the u.s. the b1/b2 is already changed here in the u.s. but to re-enter the u.s. on it you must also get the change reflected in your passport with a visa stamp that says L1A.
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