You must be an existing Comcast Business Internet customer in order to sign up for Comcast Business Mobile. If you don’t currently have Comcast Business Internet, visit business.comcast.com to get started. Here are a few things to bring with you to ensure a smooth visit: Your account number, a credit card connected to your Comcast Business account, and your photo ID. If you do not have your account number, log into My Account to access all your account information.