Airtel — amazon prime subscription along with airtel broadband

Address:

Ranga Reddy, Andhra Pradesh, 500049

Hi,
I took airtel broadband connection about 2 weeks back. The sales person promised that, if i take 6 months advance rental plan, i should get the amazon prime subscription free for 1 year. Now its been more that 2 weeks, i still didn't get subscription. My repeated call to airtel customer calls went vain. I have requested to register my complaint which they did finally on 18th april with request no 95287592. Today its 27th april without any resolution. I tried to call the customer service, they made me wait on call for 15 min then they disconnected. Not sure if the true customer service they providing. Feels really sad. What should i do?