Internet issues

Ever since xfinity supposedly to upgrade your system a couple weeks ago. I have had nothing but problems internet goes off and on the last week or so. Today was the worst internet out for a few hours then keeps going off and on since. For the past several months the internet was fine never an issue was getting test speeds over 400mbps. Since you changed things it’s been horrible. Please fix it and give me back my speed. The latest speed test was 137mbps. What happened? Your internet was just fine prior to say the middle of February. Then you started working in my area and it’s been [Edited: "Language"]. Please restore me back to what I had before you messed with it. This is unacceptable service. There is a saying if it ain’t broke don’t mess with it. Fix it!