The downside to frequently jamming out to your favorite tunes on your mobile is that, occasionally, issues with the headphone port can develop. When the headphone icon stays lit even after unplugging your earbuds, it means that the phone still believes them to be attached and refuses to switch the audio back to the speakers. This definitely causes issues with making phone calls and listening to music. Some simple steps may be able to solve the problem without too much hassle.
Turn off your cell phone and then back on. Doing so prompts the phone to re-scan its hardware upon boot-up. Often, this will toggle the phone out of headphone mode and restore normal functionality.
Remove the battery while the phone is on. Doing so causes the temporary memory cache (where the source of the issue may reside) to be dumped, meaning that when you re-insert the power source and turn it back on, the problem should be resolved.
Master reset the device if the issue persists. If the problem stems from a software issue, resetting the operating system will clear any bugs that have developed and restore the software to factory standard. Refer to your user manual for specific directions on how to accomplish this, as not all phone models use the same directions. If a master reset does not solve the problem, then it must be due to a hardware malfunction.
Contact your cell phone provider for replacement or repair options. Once all software problem sources are ruled out, all that is left are hardware issues. Unfortunately, intervention by your carrier will be necessary for further resolution. For a broken headphone port, they will either replace your device outright (if still under warranty) or educate you on how to send the phone to the manufacturer for repair.