Nokia Care - Denying to repair my mobile under warranty

I bought a Nokia mobile phone *.* on **st December from reliance digital sector **. In March month I started having issues with the mobile charging port and one day I kept my phone on charging and when I woke up in the morning I found mobile is not starting at all and it is dead. I went to Nokia care Flex services in Gurgaon. They took the mobile from me and started checking the dents and scratches on the phone and told me that this phone will not be covered under warranty as there is a small crack on the back side of the phone. They did not even check what is wrong with my mobile phone. I asked them to give the job sheet and came back. I filed a complaint against the service centre online Nokia care but not receiving any support. They said that the service centre gave you the quotation of Rs****/- to repair the phone but you disapproved the same but this repair quotation and all never happened. Also, I received the SMS saying you have disapproved the repair charges. They did not even check the fault.