Can i change employer on h1b approved petition (without stamping)


I was working on L-1B and my current employer has filed H-1B in last year 2013 in COS and the petition was approved. So i have started work on H-1B from Oct 1st 2013 but i could not visit India for Stamping so i do not have stamoing on my passport yet for H-1B.

Can i change employer on approved petition without stamping?

Please suggest your idea and experiance.

Many thanks in advance.