how to set notification tones for missed calls text messages

[AC Question]

ZTE MAJESTY Z796C I used to have a notification when I had a missed call, text or voice mail..It has disappeared and when I try to set it in notifications...no notification for any of them...If I do not hear my phone ring...or see a text message come in...the only way I know about it..a light blinks on my phone..so sometimes it is hours before I know I have a missed call...text ....or voice mail...Is there something I have done to cause this? I have had the phone for a little over 2 years...and it used to work....ant help you can offer is appreciated...