Apple India — iphone 5s-restarting intermittently, heating issue, repeated issue-second time within 1 year

Hi,
My iphone 5s (Imei[protected]) started to switch off all of a sudden and it was not turning on. After several tries it used to switch on and were also frequently experiencing heating issues, speakers was also experiencing trouble as disturbance sounds coming from speakers

This is the second time i am experiencing the same issue within this short period of time as earlier it happened as on july 21, 2017. (Raf no. Sck1325065)

I visited the nearest icare service centre in edapally, ernakulam and they said phone went to frozen state. I requested them to check and investigate the issue and replace the phone as it was under warranty. The second time as dated, 3 rd of october 2017 (Raf no. Sck1393225) as warranty exist till this month.
Even after several request to replace the phone they said it is normal software issue and can't be replaced.
Now, the same issue with phone repeatedly. I think they purposefully did not even investigate as the warranty was about to expire. And did not give an option of replacement.
I have all the documents of visit. Kindly consider my words and take necessary action