So I have an old iPhone 5s and I can't seem to figure out why I'm not hearing any sound whenever I get a phone call or a text message. The phone just vibrates when I get a call and it only lights up when I get a text. My volume is all the way up and I have checked my settings under sound and set it to doorbell ringer. The only time it works is when I am using it and the phone is unlocked. Any ideas?