Using ring groups allows you to create a cost-effective extension for a user, utilizing their cell phone exclusively. The guide below will demonstrate how to configure the ring group with an external phone number and use the ring group's extension as the user's extension. This setup enables you to easily reach the user's cell phone by dialing the 3/4-digit extension you've established. This feature is particularly useful for users who are often on the go and allows you to communicate through extension-to-extension dialing without incurring additional extension costs.