A few days ago my phone would randomly just shut off. I'd have to take the battery out and put it back in before it would turn back on. Took it to the store they said I had too many pics and the memory was low. Advised me to get an SD card and transfer some pictures. I did this. Phone was better for about a day then started randomly shutting off again. And now it will not turn back on at all. Is this maybe a battery issue? Or the phone? How much is a new battery?