Rate in GST rate

The Issue pertains to the FY 2018-19, where by we Purchased goods @ 3 % GST rate , now in October the goods are returned back to the Vendor whereby the GST rate is revised to 0.25% by the government w.e.f 1st Oct 2019.

Now the Vendor has Issued us the Credit Note dated 1st Oct having GST rate @ 0.25%

Is It correct to issue credit note @ 0.25% , and for the Balance difference (3%-0.25%) , return back the GST amount difference to the Vendor.

Please suggest