From comcast.com FAQ
but I did not get any calls from Comcast
What will happen if I exceed 250 GB of data usage in a month?
The vast majority - more than 99% - of our customers will not be impacted by
a 250 GB monthly data usage threshold. If you exceed more than 250 GB, you
may receive a call from the Customer Security Assurance ("CSA") team to
notify you of excessive use. At that time, we will tell you exactly how
much data you used. When we call you, we try to help you identify the
source of excessive use and ask you to moderate your usage, which the vast
majority of our customers do voluntarily. If you exceed 250GB again within
six months of the first contact, your service will be subject to termination
and you will not be eligible for either residential or commercial internet
service for twelve (12) months. We know from experience that most customers
curb their usage after our first call. If your account is terminated,
after the twelve (12) month period expires, you may resume service by
subscribing to a service plan appropriate to your needs.
Our practice for the past several years has been to call only our heaviest
data users, and this practice remains the same now that the 250GB data usage
threshold is in effect. We may change our practice but will, of course,
provide notice to you of any change.