Sony experia C ******* files

My Sony experia C is giving me endless problems, I had 2software updates done on my phone to resolve the problem but it's a short fix and the problem reoccurs a month after the update. I'm losing memorable photos,music and videos as the files start blurring and fading till it no longer can be viewed (changes to ******* files). my phone is however just out of its 12month warranty and the Sony experia support service are extremely unhelpful, I sent numerous emails and the response I got was to reset the ph. nothing seems to help, the software updates were temporary fixes as the problem reoccured again, there is no available software updates available for my ph as my ph already has the latest software.