Flipkart - Product is not working

We received a delivery of boat ***w sound bar on dated **June ****. The man who came to install the product says that the sub woofer is not working. We have raised a concern on flipkart app about it on *st July **** ans asked for refund. They first asked us to write a quey to us. We did that. Then they told us they will call or reply us within ** hrs. We didn't receive there reply. Then we got message that they will call us on *th of July and gave us timing. We waited but no call received and instead of that we received a message that we are postponing the call to *th of July. We waited but again we had no call and another message came that they will call on * th of July. This process they did till ** th of July and on **th of July they updated as the issue resolved by troubleshooting. And now system is not allowing us to claim for refund and saying that the refund date is expired.