cannot boot into download mode

[Android Central Question]

pls my samsung A7 cannot boot into download mode..
it all started when i did a factory reset and since then,there is always a pop ads on my screen when i ON the data and some apps automatically download without my notice,after the reset,i discovered that my phone does not have some functions again (like default internet settings) and the annoying pop up still appears..
i think that is what caused my phone not to boot into download mode...
pls proffer a solution..thks

 

[B. Diddy]

Welcome to Android Central! Do another factory reset, and this time, set it up as a new device (i.e., don't restore a backup), and don't let any apps install automatically from the Play Store. If the same thing happens, then some malware has probably been installed to the system root. In this case, you'd have to reinstall the firmware using Smart Switch: http://www.sammobile.com/forum/showthread.php?t=29914