Supply of goods regarding

We are registered in MP, have raised PO to purchase of goods , the vendor is located in Pune.

We received the goods and during scrutiny of vendor invoice, we found that in invoice vendor has mentioned Bill to us and Supply from M.P.

Also charged IGST.

as per understanding vendor has two registration one from Pune and another from MP.

My question is that in which GST Section , / Rule , vendor has transact the material?