OnePlus India — Service center Issue

Address:

One Plus Store Cannaught Place Delhi

They have taken my phone for last 5 days.Yesterday called me and said we are not able to detect the problem you can collect the phone while during submission of the phone i have shown them the problem the phone is under warranty and i have visited the Cp service center delhi thrice for same problem in last 6 months. I need the replacement if they guys can not resolve the problem