State Bank Of India [SBI] — not received cashback

I purchased smart tv of samsung from sargam electronics on 16th of april i. E. 5 months ago and not received cashback of 5% which was to be received in 3 months from the date of purchase.
As the 5th month is going on and despite of calling your customer care many times i got no solution for my problem.
I request you to please solve this problem of mine as soon as possible and give me cashback of 5%.
Hoping for a favorable response.