Tanishq — Cheating on old gold rate

Address:

560095

In Tanishq Jaynagar Bangalore on 1/07/16 I have returned my 70 gram old gold and bought new ornaments. My old gold turned out to be 89.8 % pure after melting (21.6 karat). But they evaluated the price of old gold by taking it to be 84% pure( 8% less) although it is 89.8 % pure.
This is real cheating by Tanishq.
Is there any concerned authority to give justice to consumers.
Poornima T