Go to Cisco Webex Settings and select My Profile.
Click the "…" and select Change Voicemail PIN.
Enter your New Voicemail PIN with the following requirements:
Re-enter your PIN in Confirm Voicemail PIN and click Save.
Webex | Set a Voicemail PIN (Webex Calling)
The first time you check your voicemail in Webex, you're prompted for a PIN. You may have been provided a PIN from your administrator, or you can use the steps presented here to help you create your PIN the first time or change your PIN if you forget it at any time. While you're setting your PIN, you can also do things like personalize your greeting.