A smartphone user reports that the device frequently overheats and occasionally turns off unexpectedly.

The technician should replace the battery because the cracked casing and separating bezel strongly indicate that the lithium-ion battery has swollen. A damaged or ageing battery can produce internal gases that cause it to expand, pushing the display, bezel, or rear cover away from the device frame. Battery failure can also generate excessive heat and cause unexpected shutdowns when the battery cannot provide stable voltage. This condition is a safety hazard because a swollen battery can rupture, leak, ignite, or damage surrounding components. Testing another charger would not correct physical battery expansion. Changing the phone case would only conceal part of the symptom and could place additional pressure on the damaged battery. Disabling background applications might reduce processor usage, but it would not resolve visible structural deformation. The phone should be powered off and the battery replaced using appropriate safety procedures.