Voicemail Icon Missing

I was just notified when someone was leaving me a voice mail it stated my vm was not set up. I called my vm and stated it was locked. Called my service provider they fixed the issue, along with stating this happens at times as apple and my carriers “signals” get crossed. I was able to retrieve several very important voicemails that were time sensitive. However after testing my vm from different land lines and cell carriers I was able to leave a vm but the icon did not alert me that I had new vm’s. Called vm again locked, spoke to carrier again was told the same thing but the icon is an apple issue not the carrier. Someone please help! They do offer the new vm to text for additional charge.. They get enough money already!!

TIA!!

Valerie