Usually, it's not your phone that's been hacked, but one of your accounts. But, it's more likely youve acquired some malware. What is happening with your phone?
Sounds like a malicious app was installed that has permission to install other apps (including malware). Try restarting your phone in Safe Mode: if the symptoms resolve, it's definitely an app. Then it's a matter of uninstalling apps that were installed just before the problems started. However: if the malware installed itself as a system app, not even a factory reset will clear it. You would have to take the phone to an authorized repair center and have it completely wiped.
