Terrible billing - how to rectify?

@user_mlt5v6 

My bill was inaccurate. I paid what I owed. I've had multiple agents agree that I should be at zero balance now, but I continue to get threats of being sent to collections for the 'outstanding' $136. The 'only way' to zero it out is to come back to xfinity, which I quit due to this sheer madness. I've spent well over 24 full hours in an effort to resolve this (since August). HOW CAN I GET MY BALANCE TO ACCURATELY REFLECT that I have paid all money due without subjecting myself to the incompetent billing nightmare?!?!? 

When you quit were you in a contract?  Could the outstanding amount be an early termination fee?