No Voicemail Alerts

[#1]

On My Iphone 6S  plus when I was with Virgin I used to get an alert   Maybe text ? that i had a voicemail and a little number 1 or 2 etc would appear next to te voicemail icon so i easily saw a voicemail notification  since the move to plusnet i have no voicemail  notifications  how do i get / restore these ? 

[#2]

Hi boyderoo, I helped someone with the same query recently and we sorted it by updating their phone's contact for voicemail to 555. I'd check that and see how you go on.