Whirlpool India — Refrigerator not working need a bill copy to claim warranty

At the end of last year i brought a whirlpool refrigerator from big bazaar after 3 months compressor gas leaked out and refrigerator stopped working and I lost its bill so i visited big bazaar and demanded for a bill copy but they said that big bazaar is sold to reliance group and all the equipments have been replaced so they cant retrieve bill copy and without bill copy i cant claim warranty and it'll cost around 3000 rs so i need a bill copy to claim warranty.