Sometimes your classroom or office phone may have had a little trouble contacting the "powers that be" to keep it running. As a result, you may get an error message on the display. Most phone issues can be resolved by rebooting the phone. You can do this in several ways. The first way would be to hit the "CONFIG" button, scroll down to "Reboot Phone" and hit the "SELECT" key. If the phone asks you about saving any setting or any YES/NO questions, select the YES button (you may have to select the YES button only once depending on what's going on with the phone....sometime you may have to tell it twice.) In any event, once you select the last "YES", the phone will reboot and should clear up any issues you may be experiencing.
Another way to reboot the phone is the simply unplug it from the wall then plug it back in. SPECIAL NOTE: Make sure you plug the phone back in to the SAME jack that you disconnected it from. Otherwise, your phone will not turn back on. (The jack that your phone is connected to is a special jack that provides power to the phone. None of the other jacks provide power.)