Xiaomi India — Headphone warranty

My headphones not working after one month used, as my appointment time and date i was visit (24/7/2020) service center (Sagun infotech) chinsurah 712102,
After 15-20min they called me and open my job card, and start processing for warranty claim, after 50 minutes later they told product are not available in the store, you have to came another day to collect your product. They do not have any idea value of customer's time.
When i said why did you take the appointment when there is no product, the answer is shocking for me they told me "we have no idea about our stock"!.
Till now i have not receive my product.
It is my 1st time experience and ints very very bad.