Cocacola Company — cashback offer on thumbs up

I bought 750 ml Thums Up bottle from Reliance Smart. On wrapper there was an offer of getting ₹15 paytm cashback. I followed instructions and sent unique code printed behind the label to [protected]. I didn't get any cashback in my paytm wallet. Why the cashback not received? Has coca cola become so down in market that now they started gathering customers by such fake offers? I contacted coca cola customer care through email but nobody replied to my email. I will share this incident with all on social media so that people can avoid being fool of such fake offers.