get rid of "Voicemail msg. via phone co." on my home phone screen

We have Panasonic phones which includes an answering machine for our Xfinity home phone service. 

I recently renewed my annual contract and now I continue to get this message on my phone screen: "Voicemail msg. via phone co."  How do I get rid of this message? Our Xfinity 'home phone voicemail' is turned off. So, I no longer can open up my Xfinity voicemail to manually delete this message.

Tried these two ways without success:                                                                                                                                                                                                                                          [1] Holding down the '#' key until the phone beeps. The message disappears and a few hours later the message returns.

[2] Tried manually removing the message going thru Settings:

• Go to Menu key (on top right side of phone).
• Push Menu key to go into menu options.
• Choose middle button that has CID marker and scroll through menu options.
• Find the :Settings" option and select it using the select key.
• Use middle CID button on phone to locate the "Voicemail" option.
• Click on the Select key (button).
• Find the "VM tone detect" option.
• Click on the Select key (button). The screen will show " VM detection" and shows On or Off.
• Click on "Off" and then click the right upper key (button) for Save

AGAIN, the message disappears and a few hours later the message returns.

I contacted Xfinity via chat for help and without success the autobot transferred me to a live Xfinity Agent. I was informed it would be corrected within 24 hours. That was a week ago and I never received a call back.