Very poor internet performance for the entire year

At the end of last year (12/24/2025), I bought and installed a ARRIS Surfboard S34 DOCSIS 3.1 Multi-Gigabit Cable Modem and installed it.  Until 11/17/25, I had a 800 Mbps internet plan.  On 11/17/25, I changed that to a 500 Mpbs plan. 

Today I reviewed data from download speed tests run over the last year automatically every hour.  The results are shockingly bad.  Starting on 1/1/25, there were 3,814 times my download speed was at least 100 Mbps under my paid speed tier.  When using a daily average of download speeds, there are 160 days where I was getting at least 100 mbps lower than my paid speed tier.  That means that for more than half of the year, I did not get the service I paid for.  

I imagine that Xfinity will may/will claim that my speed test results might not be inaccurate although I sincerely hope they take this seriously.  Does anyone know if Xfinity keeps records or knows the level of service on a daily basis for a customer internet service?  Is there a set up that can monitor speed test that Xfinity cannot argue with or will deem valid?  Note that I never had issues with Upload speed during this period of time. 

Here are graphs showing all the download speed tests run over the last year (no average, just raw data points), broken up into two 6 month periods.  Like I said, until 11/17 I should have been getting 800 Mbps download, after which 500 Mpbs.  

Here's a link to a Google Drive folder container 3 csv files: https://drive.google.com/drive/folders/1w5yRu4E2FSCA8PHx99yxAmJzW-rNkJ0X?usp=sharing

• All Xfinity Dowload Speeds - Raw (01-01-25 to 11-30-25).csv - This contains all the speed tests executed during this time period, including the URL to the Speed Test Results
• Raw data points at least 100 Mbps below tier speed (01-01-25 to 11-30-25).csv - This contains all speed test executed during this time period where the download speed was 100 Mbps below the paid speed tier, including the URL to the Speed Test Results
• Days where daily download average was at least 100 Mbps below tier speed (01-01-25 to 11-30-25).csv - There are days where the average download speed was 100 Mpbs below the paid speed tier

I don't know.  It's just really frustrating to be blindsided by this data!