You have multiple ways to listen and delete voicemail in our phone system. You can access the web inbox by going to https://sdircvm01.indianriverschools.org/inbox/
Once there you should see the following screen where you will log in with your district username and password.
Once logged in you have the ability to listen and delete your voicemails without having to log in via your phone.
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/connection/12x/quick_start/guide/b_12xcucqsginbox.html