LG Electronics — Phones damaged after service

I have given my phone to remove dust from its screen and also purchased new battery from lg service centre.When i got phone back with new battery it was discharged so i hardly used the battery for 2-3 minute.After returning home when i charged the battery and start using the handset touch screen was not working and next day when i go to service centre they said its not their fault and new touch screen will cost Rs1900.I have also given them Rs 400 earlier to remove dust from screen.
Name of service centre-Elcom Trading Company Pvt. Ltd.
Address of service centre - Somesh Narang,308 ,Madhuban Building , 55 . Nehru Place, New Delhi -110019.
Contact Information[protected].[protected] , elcom.[protected]@lgmobiles.com