So lately ill receive new voicemail messages without even knowing I missed a call. The phone doesnt ring or vibrate. Happened twice. Ill randomly call my cell to try and replicate the issue but am never successful at witnessing the issue first hand. Its frustrating because im awaiting a call from a possible future job and feel I cant rely on this s4 to receive calls. Both occurrences happened at home with 2-3 bars of signal quality. Do I need to just call tmobile or is there something I can try? Any help on this would be great. Thanks.