I129 Petition approved with past dates

I have received Approval notice with past dates, Approved from 10/01/2019-12/16/2019. With notice date 02/04/2020. In I797 they have mentioned I94 expiry date is 12/26/2019. Employer called USCIS regarding backdated issue, USCIS informed that they reopened my case very after the approval and recommended wait till reopen notice received. What should i do in this scenario ? Please advise. Thanks in advance.

You should keep the communication with USCIS and seek guidance of your employer and attorney. If it was a genuine mistake from USCIS, you should be fine…Again, this is a tricky situation and you work with your attorney and seek their guidance.

Its not a mistake, All the I94 expiry now is based on SOW end date.

What if USCIS REOPEN case , my current status was case reopened. what should i do in this scenario?

Not true. The I-94 date is always 10 days past the H1B approval notice expiration date…Now, the H1B approval date could be tied to SOW date.