I was talking on the phone for about 15 mins or so and out of nowhere the phone powered off and back on it has done that three times i just purchased the phone on the 26 of this month
Unfortunately I have been experiencing the same thing. I plan on using my warranty to get a better phone, this is hazardous seeing as though anything may warrant a call for help and BOOM your phone not just cuts off but powers down completely and takes forever to power back on.
Well, that doesn't look normal. With regards to call, for example here with my carrier, they have a 10 minute limit per call, you will have to dial again after that. I suggest that you take your phone back to have it check. Make sure to describe the issue so it can be resolved.