Text messages for missed calls stopped coming.

Four days ago I stopped receiving notifications on missed text, phone and email.  There was an emergency in my family and a text was sent to me early in the morning but there was nothing to show I missed a text message.  A phone call was made to my phone and again, there was nothing to show that I had a missed phone call.  Everything was working fine up till four days ago.  What has happened and what can I do to fix this?????