The PIN is used to access your voicemails and to authenticate your account. You can change your own account PIN.
Desktop & Web
Open the RingCentral app on your desktop or web browser.
Go to Settings > Phone from the left menu.
Next to Voicemail, click Edit.
Under Voicemail PIN enter and re-enter your PIN.
Click Save.
Mobile
Open the RingCentral mobile app.
Tap your profile picture in the top left corner.
Tap Phone > Voicemail.
Under Voicemail PIN, tap Change PIN.
Enter and re-enter your PIN.
Tap Save.