H1 transfer questions


Currently I m working with X company with valid visa and i94 till mar 2019. I received offer from Y company and they initiated H1 and H4 transfer.

I didn’t join Y company for some reason and I believe I got extensions for only one year i e mid of 2018 visa and i94

My question is which i94 I have to follow and if Y company do I have to apply i94 extensions? If yes what will be the process?