After the Marshmallow update, I fail to get immediate notification of voice messages. However, now I'm receiving "voicemail code error 9007" messages. Very frustrating!!!
I have the same issue and also major battery drain. This update did exactly the opposite of what it stated it would, very disappointing. =(
I found out I could retrieve the message via calling my voicemail from a landline but that doesn't help anyone if a landline is not available. Then I realized I had power saving mode on when this started happening. Once I turned power saving mode off and tested again, no more error code and able to access the voicemail from my cell
