Most carriers provide a “3-in-1” punch-out SIM card. Do not punch out the smaller sizes. Leave it as the largest size (Standard), or use an adapter tray designed for Standard SIM slots.
This usually indicates a . For example, an LG265 originally sold by Consumer Cellular will reject a T-Mobile SIM card. You need to request an unlock code from the original carrier.
The is not immediately obvious—it requires removing the back cover and battery, then locating the small metal SIM slot in the upper region of the battery compartment. While this design is archaic by modern smartphone standards, it was standard for flip phones in the late 2000s and early 2010s.
: Look for a small notch near the bottom edge of the phone. Use your fingernail to gently pry the cover upward and away from the body.