Receiving another call while on call

[AC Question]

Been using a S4 for a couple months now and really struggling with hanging up on current call to take another. The menu comes up to put current call on hold or end current call. I hit end call and then try to answer the incoming call. Sometimes it works and sometimes I can hear the new caller but they can't hear me. I even have to reboot the phone sometimes cuz my voice can't be heard on the next call I make. Am I doing this wrong or is it a common problem????