Im using oneplus 3t now. In the past I like oneplus brand devices. Becozz its operating system is simply and every thing adjustable. I used old models of oneplus brand oneplus x, oneplus one. The brand is very expensive. But facing some problems after usage of these phones. The latest android 7.0 nougat running in this brand. Os is cynogenmod, lineage, oxygen, nytrogen, hydrogen from build of this brand. Your using old models of oneplus like oneplus one, x. It is under cynogenmod. There is no update to upgrade. Cynogenmod is closed down. Oneplus store also not opening in these mobiles. With out oneplus store you cant download themes, games or open true caller inbidded. No rooms and updates avilable in this oneplus. Oneplus store closed. Cynogen mod os closed. Lineage os is worst. Oxygen os is do not have proper file zip file in downloads.oneplus.net. No customer and service avilable proper.