Bought my phone privately and got it activated through Sprint, but it now keeps telling me to insert SIM card. Where do I get a SIM card and why do I need one? Phone seems to work fine, but message is annoying.
Welcome to Android Central! In order to use 4G LTE data (i.e., accessing the faster internet speeds using the phone's signal and not wi-fi), you need a SIM card. Call Sprint about this.