If plunger doesn't remove clog, consider using chemical drain opener. For drain that's completely blocked, however, it's best not to use chemicals, as they contain caustic agents that can actually harm some fixtures. Instead, use drain-and-trap auger. To use it, remove popup stopper or strainer from clogged drain and insert auger wire into opening. As you feed flexible wire in, crank handle of device, loosening and then tightening thumbscrew on handle as you advance wire. If wire encounters something, move it back and forth while you turn auger handle. Then continue to turn handle while slowly withdrawing auger.