Log in and select your voicemail box; for "OAP CSR", select the hamburger menu from the right hand side, and select Voicemails. 

Choose your voicemail box: "online NAC customer support".

Select a voicemail to listen by pressing the play button.

If you still need to work with the voicemail, check the box and select the appropriate status.

If you have resolved the voicemail, delete the voicemail completely.