I googled "Comcast Boston" and saw an ad "Comcast Xfinity Triple Play for $99/month!". I called the associated number and the person who answered asked if I was interested in starting Xfinity service.
These reps do not verbally identify themselves as a third party vendor. It sounds like you're speaking directly with Comcast. They request a credit card number to ship the required wireless router to your address. I repeatedly asked why this was necessary.
The Comcast techs usually have everything with them when they arrive. She just repeatedly told me that she could not initiate the service request without a credit card number, "This is how we do it now". I finally relented and gave her my number. They then provide you with the actual Comcast number to call to initiate service.
When I called Comcast, they explained that this is a third party vendor not affiliated with Comcast. This company is reselling routers.