Motorola — Phone Hang

I purchased Moto G(2nd Generation) on 12th the Jan. After updating it to lollipop I started facing hanging problem.I visited your janakpuri service center 3 days back.They told me it's a problem of lollipop and will remove OS then again we will update the OS. And one day after they called me informing that phone now phone is working fine. I took a leave from my office to get my phone. And now again it is creating the same problem. Now even the condition is worse as I am not able to even unlock my phone.So please tell me what should I do? Please do something as soon as possible.