Help Phone shuts off by itself for no reason and sometimes doesn't ring

[MelonSplitter]

I've had the "doesn't ring issue for quite sometime and me nor Sprint can figure it out, but my phone just recently started turning off by itself for no apparent reason. Yes my battery was replaced by Sprint and this happens with a full charge. Any help would be appreciated.

 

[damewolf13]

If you have already called Sprint tech and had them do some troubleshooting, and that hasn't helped, then I wouldn't know what it could be.
It really seems like you just might have a defective S3. I have 2 of them and have never had this type of issue with either one. Since your phone is still under warranty, it might be worth getting a replacement.