Your extension number is not changeable and will remain constant throughout your use of RingCentral Office. As for your password, you may visit your My Profile page by clicking on Account Settings at the top of any page and changing it there. Please be aware that this option is likely to take effect immediately upon setting the new password, so make sure you have access to a computer in every location where people are calling in. If you have trouble logging in after updating your account information, please contact our Support Team for assistance.