Data Caps and automatic data shut offs when cap is reached

Will there be a way to have internet data automatically STOPPED when customer reaches data cap limit? 

It seems a bit unfair to impose a limit without also providing customer an automatic way to avoid passing the limit.  It is simply a software switch at Comcast company end to stop data to a customer when a limit is reached.  All customers know Comcast has this ability, so why can't customer have the option to have comcast data stop automatically when 1.2 tb limit is reached in a monthly cycle.  This is software programmable.    

A web page with "Monthly Data Usage" that may not display data usage in the last 24 hours is NOT an adequate tool for stopping usage before data cap is passed.