Lenovo — Lenovo k6 power screen show

Address:

Hyderabad, Andhra Pradesh, 500038

I bought lenovo k6 power on 10 january. I got an problem in my phone after 20 days. When i standby my phone for 3-4 hour. When i open it with power key or fingerprint sensor, then it take 10-15 seconds to show screen. But second time if the standby time is 15 minutes it take 2-3 second. The time increase of standby time the screen show time is also increased. I went to lenovo service center 2 times in allahabad, up. But every time they update the software without my knowledge. They are not understanding the problem. Please help me it is a big and unique issue. Please reply