• With your phone in the cradle, don’t take it off the hook, dial 2500. 
• Press the * key
• You will be prompted to enter your mailbox number (extension)
• You will be prompted to enter your password then press #
• Select #4 for Personal Options
• Press 1 to change your personal greeting
• Select 1 for Primary Greeting
• You will hear your current voicemail.
• Press 3 to erase and rerecord. 
• It will walk you through saving it after that. 
• To test it, put your DND button on and call 215-743-8963.
• Dial your extension when you hear our automated system. 
• You should hear your new greeting.

To change it back when you return, just do the above again.