Lenovo — auto restart and hanging

Address:

600084

I have purchased Lenovo A6600 plus on 23/11/2017 from Saravana stores, purasaiwakkam, chennai.From the very first day the phone hangs and restarts automatically when it is used for a long time. Saravana stores refused to replace and had asked to go to the service centre.Even after going to the service center 2 times with the same problem they were unable to solve the problem. Kindly replace the phone.