Welcome to Android Central! So was the original problem isolated to the phone's earpiece and mic, or did it also affect the main speaker (the one that plays music, sound effects, etc.)?
When you reinserted the SIM and everything worked properly, does that mean both phone calls and playing music or other sound over the main speaker? If it only has to do with the phone calls, then maybe the SIM card connection is loose or dirty. Make sure the SIM's connectors are clean, and make sure that it is pushed in all the way and snug.
08-27-2014 11:17 PM