I hope your day is going well.
Way back when answering machines were en vogue, I recall being able to check my messages remotely. The same can be done for landline voicemails.
To reach those voicemails from another phone, you'll call the phone number and eventually you'll be asked to leave a message. During that part, press the #
This will prompt you to enter in your PIN to listen to voicemails.
Let me know if this helps or not.