L G Electronics Double door refrigerator - Refrigerator not repaired after 30 days

Refrigerator stopped cooling. So we called customer care. They registered a complaint. A mechanic visited and ascertained that "the compressor failed. Should be replaced "
was his" diagnosis".
They asked us to produce invoice
We purchased refrigerator frim the LG show room. Not from any shop. While purchase concluded they promised to send the invoice by mail. But we dont received any as oer our online records
Niw company is arguing that since we dont have invoice they cannot adher to warranty stipulations .
Also from our constant enquiries at varios offices and technical repair team it is reported that
"The refrigerator purchase was not punched"
So they could not get the invoice raised.
We are at a dead end
Can your forum helo us