This is indeed caused by Message+ and simply disabling the app won't make the notifications go away. Once Message+ has a connected device, it will integrate with your phone app, so a few more steps will be necessary.
First, you need to find the remote device(s). This device can be a tablet, PC, or any device that has had Message+ or Verizon Messages installed on it.
To do that open Message+>three lines at the top left>settings
At the bottom, tap on "Manage Devices" and remove whatever device is connected.
That will unlink the device, but the remote calling is still integrated into the phone app. To remove that you will need to go to your Application Manager and clear the App Data for every instance of the Phone app.
Once you have done all that, restart your phone. You should no longer get remote call notifications.