Voicemail notification delayed
Since my upgrade to iOS9 (and subsequently 9.0.1 and 9.0.2) notification of a received voicemail can take up to 5 hours to appear. I can force a refresh by restarting the phone - after which voice mails appear. Not sure if this is a software, hardware, or carrier issue.
I've searched the support site and only found this as an issue in previous iOS versions. Any suggestions?
Device: iPhone 6+
Storage: 128G
Carrier: AT&T
iOS: 9.0.2