It was not an issue before but for about 2 month now I would get a voicemail but notification was showing up 2-3-4 hours later (that little casset icon in the top bar). If I know that the person who called most likely left me a message, I'm calling my voicemail and everything is there. And if I leave the message without listening it to the end, I will get a notification immediately. Buy it's so incovinient as I missed couple of important things already. Can someone help with it? I have Android 8.1.0 on OnePlus phone.