CELL PHONE WON'T STAY ON WHEN I TURN IT ON, IT...

Question

I CHARGED THE PHONE AND A DAY OR TWO LATER TURNED IT ON OR TRIED TO TURN IT ON AND IT JUST KEEPS TURNING OFF. NOTHING DIFFERENT WAS DONE WITH THE PHONE. WE TOOK IT TO THE SMOKY MOUNTAINS AND USED IT WHEN WE COULD LIKE USUAL. THERE WERE CERTAIN SPOTS WE COULDN'T CALL OUT SO WE ONLY USED IT WHEN WE WENT INTO TOWN. I CHECKED THE BATTERY CONNECTION AND IT IS COULD AND THE BATTERY IS FULLY CHARGED. CAN YOU HELP?