Two H1-B visas from different companies: Stamping question

I have been working for a company A for 3 yrs with end client company C. I am currently on vacation outside US for 6-7 weeks and already have a stamped visa. Client Company C wants to hire and filed for H1B right before I flew out and it is approved last week for 3 yrs(based on my approved I-140 with company A).

Issue is Attorney asked me to go for stamping as my new visa validity dates have changed so I took an appointment(as I have new I-797). But company C internal recruitment process is not yet complete and I don't have an offer letter and their process may take time well beyond my planned date of return to US. Even If I get my stamping with out offer letter(just an assumption) I can't work for the company C as my position & recruitment process is yet to start.

 

Instead of going for new company C visa stamping can I go back to US with my current company A stamped visa  and continue to work for company A and later when Company C is ready with an offer I can join them as there is a valid H1B with them?

You already seem to know the way out, that is to go back to US and work for company A till you get an offer from company B and then get your Visa transferred on Premium processing.

Thing is my Visa with company B is approved in premium processing last week. I am in India and I can’t go for stamping as company B is yet to send me an offer letter as they are yet to complete internal employment process. Question is my visa with company A is still valid (stamped recently)as I have not resigned yet and I am on vacation. I am hoping to go back to US to work with company A till company Bs process is complete and makes an offer and I can join them as I already have a Visa with B as well.