You should b able to login to your online WebEx Teams account and set your PIN code to whatever you want it to be.


Go to:  https://settings.webex.com/


After you login simply click on the "3 Dots" and you'll see where to reset the voicemail PIN, shown below:


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After you have created a PIN simply go to the Physical phone and press the voicemail button then enter the PIN code to get started.