In most cases, the SIM card itself is neither. A SIM card or eSIM simply identifies your phone line on the network. Whether you are prepaid or postpaid depends on the plan and billing attached to that line, not the chip. Some stores sell “prepaid SIM kits,” but the difference is still how you pay. To check your status, look at your carrier account or bill. If you are thinking about switching, a few things matter more than the SIM label. Make sure your device is an unlocked phone, learn what “no SIM restrictions” means, and run an eSIM compatibility check. Vouch Mobile supports eSIM on supported devices and physical SIM cards, and number porting lets you keep your eligible number.