Ridiculous charge for installation

I went with xfinity after recommendation from my apartment complex, I should have gone with Att like I should. I opted for self installation which worked fine for a day and after that it stopped working, contacted customer support which they said they will send out a tech and I asked them if this is free as I was ready to return their equipment….. they said it completely free. I went with it. Fast forward to one month after, they charged me $100 for installation that I did myself. I am dropping off their equipment, they better send me account to collections because I won’t pay their $360 early termination fee. Thank God I did not switch my phone plan to theirs.