Why does my phone only receive some calls and texts?

If my phone isn't used for an hour or so, it will not receive incoming calls or texts until I call out or send a text. I will also not receive a missed call or text notification during this time. I've checked that my blue tooth is off, my airplane mode is off, my ringer is on and the privacy setting is not on either. this is the second model of this phone that I've had and they've both had this problem.