This company is full of liars and exploitation

I have been attempting to cancel my xfinity for MONTHS.  Even after paying a "cancellation fee" and turning in my router they are still attempting to charge me for an overdue balance that I was not even at the residence for the duration of.  I was told that paying the cancellation fee would waive the outstanding balance as long as I turned in my router before August 12th.  I turned the router in and have continued getting texts about an amount I owe even though I was told that it would be waived.  I have currently been on hold for the billing department for longer than 10 minutes.  I firmly believe I have been on hold just to see if I will give up and pay the amount instead of dealing with this.  I will never be using this company again.