Do I need to go for stamping again with 2nd employee approved petition?

I have approved petitions from 2 employers( employee A and employeeB).

h1b stamping completed with employer A. But due to delay in project with employee A, I would like work for employee B.

I am still in India only. Do I need to go for stamping again with employee B approved I797 petition. please help

Thanks,

sasm