That's right, there's no "portability" for an H-1B1 (or premium processing) so if one is in the US and wants to move from one H-1B1 employer to another, he or she needs to leave and apply for a new H-1B1 visa at a US Consulate abroad through the new employer or the new employer needs to file an H-1B1 petition with USCIS. But since premium processing isn't available, the latter process would take months.