How am I being charged early term fee??

I've been with Xfinity internet for over 10 years on the 1.5Tb plan.  All of a sudden three of the last four months we went over usage and paid a ridiculous amount.  I called last Friday and after fighting with the bot agent and finally getting thru to a person he moved me to an unlimited data plan, along with a terrible streaming TV system but that's another story.  This was last Friday.  Realized this week that the NOW plan would likely be just fine with me.  I just chatted with an agent and cancelled my Xfi internet and TV plans.  They then inform me I have to pay a $120 early termination fee.  This is absolutely CRAZY and unfair.  Ten years I have been paying, I guess since I went to unlimited data I was automatically put in a contract?!?!?  It was never mentioned to me.  He text me a code he said I needed to approve the change.  Maybe that mentioned something in small print, but shady, sleazy and unacceptable.  This was NEVER MENTIONED TO ME>.  Not to mention he changed me from DVR cable to the dumb streaming ZUMO [Edited: Language].  Again, he never mentioned that it was little streaming boxes that are cumbersome, slow and not user friendly.  Can I get help with this criminal early termination fee?!?!?!