Store employee forced plan change.

I had an $85/month internet plan for 2gig, locked in for 5 years.  Last night I made changes to my tv package, resulting in a new monthly bill amount of $234.31.  They had me go to a store to swap out my cable box.  In order to swap the box, the rep sent me something to authorize on my phone.  It wasn’t at all clear, but it said, new estimated monthly bill amount $253.77.  I stopped him saying that it wasn’t right.  He said, “ok, let me  fix it”, and then sent the same thing.  I told him clearly that I wanted no changes.  He said, “sign it and then I will fix the price back to what it was”.  I said, that I wasn’t comfortable with that, and he said, “your tv won’t work and I can’t help you if you don’t sign it”.  So I signed it, and then he played with it for a few minutes and said, “yeah, I think the numbers they sent you last night were wrong, the $253.77 is the best I can do, sorry.  Call customer support and have them fix it.  At that point, I’m frustrated, but called customer support.  After literally an hour, the “loyalty” rep told me “man, this is so messed up…the agent in the store locked you into a 1gig plan for $20 more per month.  There’s nothing I can do on my end.  I can’t get you back to your old plan, but that guy [Edited: "Profanity"] you big time!”  This all took place in less than 24 hours, and it clearly was not a “mistake” on my part.  The phone rep acknowledged that.  He said no one would want to do that!  So my internet speeds are now half as fast, and I’m going to pay $1,200 more over 5 years due to this rep either [Edited: "Profanity"] or worse, intentionally changing my plan for the worse.  The only reasonable solution will be to have my old plan reinstated at the correct price, or I guess I’m done with Xfinity forever!  What can be done??