Formal Complaint – Unexplained Data Usage, Unidentified Devices, and Poor Customer Support

I am writing to formally lodge a complaint regarding an unresolved and serious issue with my Comcast/Xfinity internet service, along with the inadequate customer support I’ve received in trying to address it.

On a single day in early June, I received a usage alert stating that I had already used 75% of my allotted monthly internet data—in just one day. This is highly abnormal, as my household setup has not changed at all: same number of people, same devices, and consistent usage patterns. I immediately contacted Comcast support to understand the cause.

Instead of a proper investigation, I was told not to worry, as I wouldn't be charged for data overages this month, but I would be starting next month. This completely misses the point. I wasn’t asking about fees—I was asking why such a massive spike occurred, what device was responsible, and how Comcast could not provide an explanation despite me using their own modem.

When I pushed for answers, I was told to “just sign up for unlimited data.” This is unacceptable. Why should I be expected to pay extra for a service I don’t require, especially when the root cause remains unexplained and may stem from Comcast’s end?

While troubleshooting, I discovered 10 unknown devices labeled “CTDI CMTX” (which appear to be Comcast-related) showing up as active on my network. I have no knowledge of what these devices are, how they appeared, or why they are consuming data. Comcast agents could not explain their presence or verify if they were responsible for the usage spike.

Since then, I have spent hours on phone calls and chat sessions with multiple agents, providing the same information repeatedly. I have screenshots proving that:

• Agents did not read prior case notes, or claimed they didn’t have access to them.

• I was asked irrelevant questions (e.g., “Is your internet working?” “Is this a billing issue?”), despite a case already being opened.

• I was forced to repeat my name, address, and the entire issue from scratch each time, despite referencing the case number.

• No effective escalation occurred, and I received zero follow-up from anyone with technical authority.

This experience has been incredibly frustrating, inefficient, and reflects poorly on Comcast’s customer service systems. A case should serve to prevent repetition and escalate unresolved issues—not force customers to chase down answers for days.

I respectfully demand the following:

1. A full investigation into the unexplained data usage on my account.

2. An explanation of what the “CTDI CMTX” devices are and how they appeared on my network.

3. Confirmation that no unauthorized access or data usage has occurred.

4. A summary of all case history and actions taken.

5. A written resolution from Comcast acknowledging the issue and outlining how it will be addressed and prevented going forward.

If this matter is not resolved promptly and transparently, I will escalate the issue further by filing complaints with the Federal Communications Commission (FCC), Better Business Bureau (BBB), and Consumer Financial Protection Bureau (CFPB). I am also prepared to share this story publicly, as the hours of time wasted, the lack of accountability, and dismissive treatment are simply unacceptable.

Sincerely,
Binny [Edited: "Personal Information"]

Case #: [Edited: "Personal Information"]