I have 2 - one in my desk at work, the other in a drawer at home.
They're just old Nokias that used to be mine with PAYG SIM's in now.
Nothing particularly suspicious about still having an old phone lying around - except maybe that it's charged (though turned off), but I could bluff past that one with amazement about the battery life of those old Nokia.
I had to use one a few years ago when I broke my phone, so I have reasonable excuse for keeping the thing.
All call history & texts are immediately deleted.