The process android. process.media has stopped working

Hi, I keep getting this message when I try to put on / change back to my ring tone :

the process android. process. media has stopped working. It started when I was trying to knock off my data and my screen went black and has been like that since. The phone is an Alcatel Idol 4 but no option in the device section to pick it

I have no sound when I get phone calls and keep missing important calls

Please help

Thanks in advance