¿Why real vendor is not update in BSEG table?

Hi MM group,

I have an scenario where the vendor that I chose in PO change when I do the invoice verification, and when I bring the vendor in table BSEG from LIFNR field, it shows the vendor from PO and not from IV. As this is a FI table it is suppose to shows the IV vendor. Why it is not?

This image is from BSEG table, and the vendor is the code 800001585

This is the FI document when we can see that the vendor selected was 800001648

I need to show in the report the final vendor not the vendor in PO, so if i read the BSEG table i will show incorrect info