Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If the voicemail service is actually provided by your phone service provider and not 'in' the Panasonic phone itself, then you have to follow procedures appropriate for that voicemail provider, to erase messages.
If the voicemails are in your phone itself, then that's a different case.
The model # ***** have stated does not appear to have built-in voicemail by first indications, upon checking the manfuacturer's data sources on that model.
Please let me know more about the case, so that I may advise you further.