As could be reattached the back part of the phone.

Er, I am a bit confused as to what you mean. If you mean the oval in the center of your phone which contains the light, camera, and Motorola logo is coming off, then you may want to call Motorola and ask them, as this should not be able to happen. If you mean the back cover (piece of plastic), yeah, it's detachable. You should've gotten a guide on how to do that upon first activating your phone, but if you don't know how to, just run your fingernail under the cover around the edge of the phone. It should come off. Then align the hole in it with the piece in the middle and press it back in. Make sure to press around the edge and the center, that's how it keeps water out of the SIM card and SD card slots.