H1b stamping with old employer or new?

Hi All,

I am currently on an H1B from Company A and is valid until 2021.

I got a new job with Company B and they had applied for a transfer using premium processing. I have the receipt number and will get the i797 in about 15 days.

I had to travel to India due to an emergency.

Now my question is: To book my appointment for H1b stamping should I take documents from Company A. The company I currently work for or Company B (Company that has applied for my transfer and I am still awaiting Documents).

I am looking for help asap. Thanks in advance.

Thank you