Poor repair and non communication with faulty Tab3

In 2014, while still in warranty, my Tab3 wouldn't switch on. Still under warranty, I took it to the smart care centre. The entire operating system had to be replaced and despite asking that they notify me if I needed to do a backup, they didn't and ALL my files were lost. In April 2015 it again started acting up - freezing, the \back"button wasn't working"