I have this same problem. Was on the phone with Carrier (ATT) and she said my settings are correct. She even deleted them and re established and still no visual voice mail. I get a big blank screen that just says in a tiny box "Call Voicemail"???
I was running 11.1 (public beta) and noticed after I got off the phone with carrier that 11.2 was available. Downloaded/installed. No change.
Any other ideas? Thanks!!