H4toH1 COS which I-94 to be used for applying SSN

Hi,

I had applied for my H4 to H1 COS in this year 2014-2015 and got my H1 approved nd is effective from Oct 1st. I have travelled to india for a week in the month of September and came back to US on September 12th. Now my I94# has changed since i exit and renter US.

My query is while applying SSN which I94 should I be using, Since the approved I-797 has my old I94#. What should I be doing now?

Also how many days before my H1 start date should I be applying my SSN?

You cannot get SSN with H4 and your old I94 which is used for COS is no longer valid. You will have to apply for an amendment of H1 using new I94. Once your amendment is approved by USCIS, you will use your new I94 for applying SSN