Flipkart — Used product delivered and return was delayed and spoil my business by giving fake pick-up schedule

I ordered a iphone 11 128 gb in Flipkart by using 35000 on Flipkart pay later and 6519 by card payment. They delivered a product on October 5th 2022. There is no seal in the box. There is a seal only in the wrap cover. By checking the serial number of the product in apple warranty, the support remains around 3 months only. So the product was used around 9 months.
So I try to return the product. I made a return request and there is no option for refund. So I called customer care service and inform the same. The executive cancelled the request and placed a new request with the reason damaged item. The executive told me to contact after 9 am to talk to higher authority and escalate further to proceed fatser. I called to reach but they told call after 2 hours. After that They told me to wait around 11 days. I was waited on the call for 1.30 hours to talk to a higher authority person after that also they are not available. And made around 10 calls in a day. The next day an executive said that "you raised as damaged product so only your request was still in pending" and i cancelled the request and place a new request and intimate the executive that I need to go out for a business for 4 days and I am not available for the next 4 days. They didn't hear that and repeat the same script to wait till October 13 th 2022.
The next day they accept the return and called me for pickup. I clearly told the pickup agent that I was not available in the city and come back on Wednesday october 12th 2022. On October 10th, an agent called me for pickup and told that the return request will be cancelled if you are not handover. I said the reason and he told that I will reschedule for tomorrow.
On October 11th, i received a message for pickup before 7 pm, till 6.40 pm i didn't receive any calls, I called the agent and ask him for pickup, he said that I will reach the spot in sometime. Then only I committed my work out of the town for 3 days. But he came and went back by throwing a reason like I didn't pickup iphones. There are other agent to pick up this. He will contact you tomorrow.
Like this, Flipkart spoils my business and affect me mentally. Make me a mental depression.

And the seller, sold this product without providing a proper gst invoice to claim input. I think, the seller and Flipkart purposely avoid gst invoices to sell products like this in offer sales.