How Is this possible?

What to do? My phone and pad Is hacked, and i have reset them both In factory settings many many times, but that does not have helped. I don't know Is It only one person or many who are constantly harrassing me, but tell me how It Is possible, that i bought a new phone and it did not take long (one day) and somebody was hacked the phone. I have notice that every app and especially system apps have long list of permissions, and it Is very clear that the hacker has increased permissions the way that he/she can spy me better. So, any wise thoughts, what should i do?