Hi debfromwilliamsburg,
Thanks for reaching out to the Apple Support Communities. We understand you're not seeing notifications when you receive a new voicemail, and we'd be happy to get you pointed in the right direction.
To start, have you only noticed issues with notifications with your voicemails, or have you experienced any issues with notifications for other apps as well?
Let's have you check to make sure that you are all set up to receive the notifications alerts on your device: Use notifications on your iPhone, iPad, and iPod touch
Also, check out the steps listed in the following resource under the section, "Get help with Visual Voicemail" that may help: Set up Visual Voicemail on your iPhone
If still having issues after those steps, and if the issue is only affecting your voicemails, we'd recommend reaching out to your carrier as voicemails would be a carrier feature on your device.
Let us know if you have any other questions; we'd be happy to help.
Take care!