Urgent !!! Procedure to apply COS from H4 to H1


My indian employer has filed my H1B petition and it is approved. As of now, I hold H4 visa to join my spouse at onsite.

I would like to know if there is any procedure for change of status from H4 to H1, so that I can initiate my visa processing at US itself.

Also, can this be done by self or only US employer (who will send me an offer) can do this.

Any suggestions in this regard would be of great help.

Thanks in advance!