Letter from NVC for past GC case. Already acquired green card.

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Hi, 

I had multiple GC Petitions EB3 -> EB2 (Promotion Same Employer) -> EB2 (Job Change: New Employer) . Recently, I received letter/notification from NVC to pay fee for the case which appears to be related to very first EB3 petition but I already received my green card few years ago with EB2 (related to New Employer). Posting here to figure out if you experienced similar situation, and what step you took. 

Thanks in advance.