Apple - Faulty device sold and no help received

I bought Apple Iphone * with Model number MN***HN/A * years ago.Since the day i bought my phone ( for around Rs *****), the phone has been giving so many problems. It keeps restarting. It also gets stuck on lock screen and nothing happens for some time no matter what you do. Sometimes the phone does not connect to internet ( Wifi or mobile) for some time even though wifi works on other devices. I called Apple company and told my problems on *nd day of buying my phone. They told me to send them data from my phone. I did what they told me. In further telephonic discussions, they kept telling me to send data again and again which i did. I also sent them several emails to which no one gave satisfactory response and sometimes no one even responded. Then i went to local Apple authorised service center. They told me to do factory reset of the phone. I already had installed too much data on phone but i still did factory reset and lost all my data. I asked the apple executives to replace my phone as clearly they had sold me a faulty device for a very hefty amount. But they denied my request. This kept going on for a while. Later on they started telling me that the problem is in software and the problem would be fixed in the next update. I updated my phone everytime an update was released but i kept facing the same problems. This kept going on and even after * and a half years, my phone kept giving me the same problems.
Last week IOS ** was released. I put my phone on update at night and in the morning, the phone stopped working. Only Apple logo was seen and then the screen became blank. I went to service center and explained the whole issue to them with the history of my complaints. They told me that I would be charged Rs **** as service charges. Then I called Apple customer care and explained the whole issue to the executive. She asked me to give the phone to service center people which I did. Then they talked for about ** mins after which the service center executive gave the phone back to me. The apple executive told me that the service center executive has confirmed that there is some problem in hardware and the phone was not getting connected to their computer. Then she transferred the phone to her senior. I again explained the whole issue to her with history and requested her to solve my issue. She asked me IMEI number of my phone which I gave. Then she confirmed that she has found the case ID which I raised in ****. She told me that she has to to do some investigation and she will revert to me on Monday. I waited till Monday. I received a call on Monday. In the call, she told me that she cannot do anything and the only thing she could do was to raise a complaint against the service center. I requested her to either repair my phone or replace my phone. She denied my request.
The phone had hardware problem since the beginning but Apple company onlyaccepted this fact after * and half years after the warranty was over.I have been so much tortured with the whole experience even after paying such hefty amount to buy the phone. I request to take action against the company and bring justice to me.