H1 transfer with pay slips

[cool2k7]

I work full time for a company A in India. Recently, I had an offer from a company B in the US, for a consulting position, which I accepted. Company B filed for my H1B visa, and it got approved. I have scheduled an appointment at the consulate in Bombay for stamping. Now, when I tried to resign from my current company A in India, they coaxed me into not leaving. They [Company A bosses] now want to file for an H1B transfer and want to send me to their USA office. But my question is: Since am still in India, and have not started working for Company B on whose name the petition was approved, I do not have pay stubs. Is it possible for me to still get H1B transferred to Company A? If so, how? Also, if I go for the scheduled appointment which is 2 weeks from now, and meanwhile my H1B transfer gets approved, what do I do? Can I enter the US with the following: company B's 797 approval and the corresponding stamp on my passport, but with a new H1B transfer approval letter, in the name of firm A? Or should I cancel the appointment for stamping, wait for H1B transfer approval filed by company A [if it's possible to transfer], and then schedule a new appointment for stamping.