Have Samsung Galaxy S5 and cannot get Visual Voicemail to show

[AC Question]

Have tried more than one voicemail app on my Samsung S5 and to date cannot fine even one that gives me a "notification" if I have a voicemail waiting or at all. My text messages as well as phone apps have a small numeral on them when I have received a text or phone call. HELP !!!! MY PROVIDER IS ATT AND SO FAR ALL OF THEIR REPS HAVE BEEN UNABLE TO HELP IN THE PAST TWO YEARS. IN FEB., I PLAN TO SWITCH TO A NEW PROVIDER BECAUSE OF THIS PROBLEM THAT HURTS MY BUSINESS.