A few things to try if you feel like your phone is have issues that seems to continue even with a new phone.
- Call your service carrier and request a new simm chip. When received in the mail call them to assist you with a password to lock it from being tampered with. Don’t lose the passcode!
- check to see how many cloud storage services you are using. Change the passwords on them to make sure someone else can’t use the service to upload files that can be synced to your device without your knowledge.
- think about backing up all your files in your cloud account to a thumb drive and starting a fresh file system with only the files you currently need. I have done this in the past to find that a it fixes the issue. Probably a old corrupted file causing issues or one created with an app I’m no longer using.
- if really worried keep your phone off of networks and keep the blue tooth shut off. Then under your cellular settings you can shut off permission for different apps to transfer data unless using Wi-Fi. Keep banking apps and other apps that contain important information turned off until you need to use them. That creates a firewall like access using cellular access options.
It can be hard to tell if you have a bug or something more serious. If worried then just really get to know all of the settings and lock down anything you feel might be used to compromise you just to be safe.