Kisna Diamond Jwellary review: less weight found than mentioned on certificate issued by the company

Purchased diamond jwellary worth 63500/ from local shop keeper under KISNA DIAMOND JWELLARY brand name.

After verifying the weight mentioned on the certificate issued by the company it was found that it is less.The weight mentioned on the certificate was 8.88 grams where as i found it 8.56 grams only.This is a clear cut case of cheating by this KISNA DIAMOND JWELLARY company.

Now I want to register a complain against this company pls guide me what are the norms and rules to lodge a complain.