So glad I found this thread! I had Comcast pull my credit WITHOUT me giving my SSN! I gave my name and address and I'm assuming they were able to find it somehow.
All I wanted was information on new service! I told him I would pay the $100 deposit rather than a hard pull - but again I did not even sign up! Then about a month later, I received a call saying my installation could not be completed because they had not received my $100! I told him I didn't want the service, had never signed up.
Today I see they did a hard pull on October 12! Unbelievable! I tried calling - that was a lesson in frustration.
I will follow the advice posted and report back.