Hi and welcome to JustAnswer,
Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, who is your phone service provider please?
There are two (2) services that provide the same answering feature; 1 is VoiceMail provided by AT&T and the other is built-in into most models of Panasonic.
If "...voice mail on this phone...", then this would be the built-in into the Panasonic.
Bear with us; re-confirm and post back with the complete model number of the Panasonic please.
Please verify; KX-TG95428
Panasonic models would only have 4 or less digits after the TG; something like KX-TG5428.