Did this beeping occur after you downloaded an application? Because sometimes applications can cause different functions on your phone to malfunction. How long have this issue been going on?
I'm having the same problem. I've had this phone for over a year (Samsung Galaxy S5) and this beeping only started a couple of weeks ago. It is a "double beep" like some is trying to beep through on the phone call, but no one is. It happens every couple of minutes and on all calls. I don't THINK I've downloaded any new apps recently, although the phone continually "updates" my current apps all the time. Is there a way to tell when apps were installed so that I could explore that route? My husband has the same phone (and a lot more apps), but he hasn't noticed a problem with the beeps.