how to file a complaint

3/25/2025
Boston

Dear Sir or Madam,
I am writing to address the internet service provided by your company.
I have been with Xfinity since 2022. Initially I was with 500 Mbps internet. Six months later I subscribed to 1 Gig. The tech support stated that the router I have was sufficient for this speed. More than a year and a half I was using this service and when I measured the speed to around 500 Mbps I was told by the tech support that this is due to the high traffic and use of the internet in my household. Recently I was offered a 2.1 Gig  connection with a minimal increase of $5/month for a year. I asked the rep about the router and after the check of the model the answer was that I do not need a new one, so I agrred with the new speed. I measured the speed afterwards and it was again 500 Mbps. I was about to call again but instead I visited the Xfinity store where the clerk asked me right away why I did not bring the old router, since the capacity of it is 500-600 Mbps.
I was paying for a Gigabyte and using Megabyte router for more than two years despite my several inquiries about the speed.
I think that this is not how an otherwise fine company as Comcast/Xfinity should treat customers and I expect some sort of retribution or I will turn to BBB for lawyers to seek advice. 
Sincerely,
Todor [Edited: "Personal Information"]