Unusual battery drain
Phone gets hot when not in use
Strange background noise during calls
Calls dropping or connecting oddly
Delayed shutdown or startup
Unexpected data usage spikes
Random pop-ups or apps you did not install
Text messages sent or received that you do not recognize
Microphone or camera activating unexpectedly
Poor call quality in places where it was previously normal
Device behaving strangely after installing an unknown app or profile
Settings changing without your input
Account login alerts you did not trigger
Contacts receiving messages you did not send
Phone lights up or restarts on its own
SIM card issues or service interruptions without cause