Data Usage Spike

I saw on a forum thread from about a year ago that xfinity had a known issue that was resulting in incorrect data usage calculations.   Was that ever resolved?  Just like many others have reported, my data usage has doubled within the last 6 months.   The frustrating part is that xfinity does not provide it's customers with a means to monitor usage by device so we are forced to trust your data,  which I'm finding difficult to believe.   Upon contacting customer service regarding the issue,  the representative's solution was to repeatedly suggest that I pay for unlimited data.   Not acceptable until I understand what is driving the usage spike