Here is the situation.
I have my H1B approved from a consulting firm. But I do not have the recipt or the I797 with me, they have them.
I am on OPT and my OPT expires sometime in Sept., right now I am working for a company on my field of study. They are now willing to sponsor me.

What would be the best move for me.
Transfer H1B from dhoti to this company before october?
Apply for another H1B thru' this company? Can I ?
How about extending my OPT for I fall under STEM?

Any helpful suggestions or similar situation ideas welcome.