I have a valid H1-B visa stamped on my passport till November 2011from Company A. I joined Company B in July 2009. I have got my Company B approval notice I-797 from USICS.

Due to emergent need I'm travelling to Pakistan in October for a one week vacation. I have my approval notice from Company B and the visa transfer is done. My new approval notice is till June 2012.

My question is do I have to go for stamping when I go to Pakistan because I changed companies even though I have a valid visa from my previous company and an approval notice from my current company?

I will highly appreciate your help in this regards.