I had a similar problem. I phone XR with 64 GB of space. On the iPhone Store menu, there has a space of 30 GB. But iPhone always showed a message that is running out of memory. When someone calls me through Whatsapp, I can't pick up the call and the call suddenly dropped. When I access the photo, the quality of the picture will be reduced, and I can't take a picture with the error message that iPhone running out the space.
Every time open Whatsapp, the apps only can be accessed for a few seconds then off.
Does someone here have the solutions?