A couple of months back I purchased a Samsung Galaxy S4 with high expectations. But I found that the quality was really poor. First of all the signal strength was very poor that I could never even once place the phone on the ear and talk.
Always I switched on the speaker and saw there were more lines present for the signal and then talk. But when using another phone at the same spot there was no problem at all. After few days, the phone would automatically switch off and then automatically become on again. I could never speak properly with anyone as it had high voice distortion and the volume was very low. Finally I stopped using it.