I can relate how Comcast is handling this for me:
I have been a Comcast customer in MA for over 10 years. Recently I received a collection notice for Comcast services in Chicago. I have never lived in Chicago, nor have I ever authorized ANYONE to use any Comcast services there.
After contacting Comcast Customer Service, they verified that the collection notice was legitimate for a past due balance in Chicago. After asking Comcast to view my current and past Comcast account in MA, and explaining that I don't live in two places at the same time, Comcast "mailed" me an identity theft package. They want a copy of my license (or other goverment issued id), proof of my residence (mortgage, utility bill, etc ---but NOT a Comcast bill), and require my name, address, date of birth, SS# and description of fraud. They also require an affidavit (notarized) that contains all this information be sent back to them. Supposedly I will be contacted by them after I provide all this information.
Seems they've already proven that they can't be trusted with all the data necessary, as they granted someone in Chicago services without validating that individuals actual identity, but what other choice do we have?
You would want to contact Customer Security Assurance Team to have this investigated. Below I have provided their contact information.