Being charged $250 for equipment after I was told no cancellation fee and I returned my wifi device

Xfinity costumer service has been a nightmare, waiting hours on the phone and getting charges left right and center. We got xfinity wifi for our apartment in July and cancelled last week because of insane charges and costs. When plugging in device to ethernet we received no wifi, called to get it fixed and ended up paying for a technician. Which we said we do not want a technician if we have to pay for one. Regardless they charged us, I cancelled our wifi for the next month. Then after returning the devices and cancelling I got a $250 charge, that I was not told about AT ALL. I cannot afford to pay this charge. After calling they gave us another excuse, but since my card was used for autopay I am stuck paying this fee. This is completely ridiculous and extremely unprofessional.