Crossbeats — Not getting service support

I have purchased one pair of TWS earphones (Model: Enigma) from the company named Crossbeats in the month of June. Since then, there is not a single day when the device worked fine. There are multiple issues with the device. I lodged a service request, and they suggested some steps over email which did make any difference. The device is still under warranty. So I was told to send the material to their Bangalore service centre as they do not have any service centre in Kolkata, that too at my own cost. After almost 10 days I got the material back stating the problem is solved, in reality which is not. Then I contacted the service centre they again asked me to follow some steps remotely and again I was told to send the material to them at my own cost. I refused to spend another Rs 300 shipping, and I asked them to take the material back and refund me. Moreover, I was not provided any invoice for the material I had to ask for the invoice.