Lavie - Warranty not honoured

I purchased a Lavie backpack in March and the strap broke within * weeks - not from tear but just the poor quality stitching breaking. I submitted a warranty claim and after many repeated followups, it was finally accepted long after the promised time. Then they told me they couldn't replace the product because it was not in stock - a blatant lie as it was clearly available on their website itself. Since then, I have been requesting them to send me the replacement product or refund my money but they are doing neither and ignoring all my communication.