Two things...
First: Did a quarter million Comcast subscribers actually go so late on their bills that it made sense to send them to a collection agency? Or is this like CenturyLink calling me and threatening me with collections because they claimed I was 2 weeks late on a bill, for the first time? (I had paid over the phone with a CenturyLink rep, but apparently it didn't go through and they didn't tell me. That phone call was the first sign that they hadn't received the money.)
Second: Never provide your social security number to any company outside of the banking industry. Period. Your doctor's office doesn't need it, and your phone/broadband provider definitely doesn't!