On most phones, a red light indicates a message in voicemail. You need to press the MESSAGE button and follow the instructions on pages 4 and 5 of this reference manual.
https://downloads.avaya.com/css/P8/documents/100130184
Have you tried to retrieve any message? Sometimes another extension will set the MW light on inadvertantly.
Calling the VM won't help but if your retrieval attempt keeps ringing it will be a phone somewhere within the system. FIND IT & Answer the call at THAT extension and the light should go out. NB sometimes there can be more than one in Queue. Panasonic stack up to 8.
This is done via the Avaya Manager program on the PC that is administering it. The Main system Password can be hacked and reset but it takes special equipment and training.
If you can't get in normally, I say time to get an onsite tech.
hi robert.
see if this helps you,if not go to the link and the bottom.
How to change the display name in Avaya phone?
Press the Select soft key or the OK button or the right arrow key. Use the up and down arrow keys to scroll the display to the option Display Name. Press the Change soft key to change the setting or use the left or right arrow keys. Display your extension number and the date and time on the phone when it is idle.