Corroded Lightning cable

The pins on the lightning cable that came with my iPhone 7 are damaged and my phone charges only when I use the cable on one side. I have included photos. The pins seem to have corroded due to poor material or gotten damaged due to arcing owing to a lose fitting connection with the charging port. In any case I see this as a defective product. My phone is within warranty however Apple has refused to replace the cable. When I took it into the service centre in Pune, India, they refused to replace it. I'm not happy with their decision. I can see loads of cases on the internet where apple replaced the lightning cable within warranty no questions asked. Apple refuses to escalate my case and say that their decision is final. Any suggestions on the causes for this damage (is this common?) and how to escalate within Apple will be helpful.