Kalyan Jewellers — Can't purchase gold coin with Jewellery voucher

Address: No. 732/1, opp. Chhadawad Police Chowky, Ambawadi, Ahmedabad, Gujarat 380006

I purchased the e-voucher of kalyan from my HDFC Bank against he credit card points. I go to the kalyan Jewellers Ahmedabad outlet, he says you can not purchase the Gold coin on these voucher. On HDFC bank side there is no T&C details. I am adding of photo of that guy who is responsible for these.