"Iphone is not activated" error

I have this Iphone 6s about 4 years and use it every moment of my day.today suddenly it shows "Iphone is not activated" in the screen and then my carrier became "no service".it gets okay when i restarted my Iphone but after a while it shows up again and again.please help me with that.

some one told me check the report on "3utools" application

at the bottom of that application report it wrote on red "this device is disassembled"

whats that mean and what should i do??

whats going on?

this was the error i've got

and this is the "3utools" report :