The velour pads of my DT770 gave out due to a manufacturing defect. I emailed them at
Indiaoffice@beyerdynamic.com. They asked for invoice copy and requested me to ship the headphones to their Bangalore office. I got them back with new pads after a week. All communication was done via e-mail only so I'm surprised that you did not get any reply. My unit was also purchased on Amazon.
I originally found the above email ID on HPZ. I checked just now and they seemed to have updated the contact info:
Beyerdynamic Warranty Claim & Service in India - Headphone Zone
Contact details listed in the signature of the person who handled my case:
Deexith HM
Assistant Manager – Pre Sales and Technical Support (India)
Mobile : +91-9008602441
Fixed Line : +91-80-23310101/02
Email : deexith@beyerdynamic.com