Error when trying to add unlimited data using own modem

Hey there @samayoa45, thank you for touching base with us here on the Xfinity Support Forums. I've let the teams know that there was an error when adding the Unlimited Data via the website, and they can look into it further.

As a note, for the states of CT, DE, MA, MD, ME, NH, NJ, NY, PA, VA, VT, WV, the District of Columbia, and parts of NC and OH the 1.2TB data Usage Based Billing plan is not in effect ergo Unlimited Data is not currently being offered. If you live in any of these states, The 1.2TB Data Usage Plan has been deferred until January of 2022: Xfinity 1.2TB Data Usage Based Billing Information

If you live in any other state, and you're having issues adding the service, we can help out. I invite you to send us a peer-to-peer message with the account information so we can build the order for the change. I'll leave information below on how to send us a peer-to-peer message.

To send a peer-to-peer chat:

Please only send a chat when requested by an official employee--sending a chat when not requested may result in the chat being lost given the high volume of chat requests received daily.

• Ensure you are first signed in, then you will see an icon at the top right of your page. Click that or follow this link: https://comca.st/3l6FEXb
• From there, click the 'New Message' icon. In the 'To' field, type 'Xfinity Support'.
• Type your message in the text area that appears at the bottom of the window and hit enter to send. An official employee, such as myself or whoever is first available, will respond.

We ask that you please include your name, the account holder name (if different), and the service address alongside your inquiry so we can best assist. 

Concern moved here for greater exposure to actual Comcast employees for assistance.