Xiaomi India — Mobile phone service

Dropped my phone Redmi Note 4G on September 8th 2015 which damaged my phone display . To rectify it i gave it to Vinayaka Communication a authorised service centre in Coimbatore, Tamilnadu mentioned in Mi India web site. They charged me Rs 4250 for changing the display & took two days .When i went to collect my repaired phone i found the sensor is not working.(By poor workmanship of service centre) When i enquired about this they checked & told, PCB(Mother board ) should be changed . I said, It was working properly when i handed over so its your responsible to give it back in same condition . For that they said, we will claim for warranty & replace it. Now its been 20 days after all this days they are saying a same reply which is, we are waiting for the spare from the company.