i think your phone has virus problem try these steps .install quick heal antivirus .full scan .if it rise any virus in installed app or apk then uninstalled it immediately .and restart your phone
i also survived this kind of situation so i know how to deal with it.
huge problem ...thats the deal with Samsung they dont even replace their faulty phones .move to apple man..i was planning to pre book note 8 today buy or s8+ but looking at how laggy my s7 edge has become in just 1 year with buggy software updates i just cant take it ..hope people learn and samsung modify it policies with faulty phones.
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