I am using this mobile from June 2015 onwards. This is best mobile in this segment.Previously its OS is Android Kitkat 4.4.4 at that time this phone facing low speaker volume. Now upgradation available for Android Lollipop 5.1.1. After upgrading low speaker volume issue solved. After upgrading first 1-2 hours it’s have some lag now Its working smooth.but this phone not support OTG function.and overall is a good phone.