I am in Australia, and this is happening to my husbands Galaxy Note 2 as well. It is driving him crazy. He relies on this phone for his business. Customers call him, the phone does not ring, it goes straight to voice mail. Then because the customer cannot get him (he is an electrician), they go to the next ad in the paper and call someone else. Result: lost work.
Powering down the phone doesnt fix it, and it happens whether or not he is on another program like internet or email. I have been with him at night, with the phone on the table in front of us, and seen it light up with a missed call, yet it never rang!!
We took it into the shop we bought it from, and they said it was the internal aerial - they sent if off for repairs. After 3 weeks, we got phone back, it seemed to work good for about a month, but then the problem returned.
Our carrier is Telstra - the main carrier in Australia. Before that we were with Vodafone, and the problem was worse and the reason we changed to Telstra, thinking it was the carrier.
We are considering going over to an iphone, which for us is a major decision, as we hate Apple and refuse to have any apple products in our house!
Any advise would be appreciated.