My Iphone has been hacked
I am using an iPhone 6s; yesterday, the device lagged, and I could not control it. After that, it is controlled automatically by someone he/she tries to access my message and my phone number list. I have changed the Apple ID password and reset the device. However, today it is controlled by another again. He/she accesses my camera and keeps switching the front and rear cameras.
How could I fix and avoid access to other applications like a bank application and other important ones?
Thank you.
iPhone 6s, iOS 15