I've asked a Comcast employee to help you. You should expect a reply in this thread.
Hello Comatthew, Comcast can pull your credit w/o your permission as we have a legitimate business need in connection with a transaction that you initiated. If you feel as though this credit inquiry was made without your knowledge and permission I can look into having the inquiry removed. Please send me a private message with your full address, account number, and the name on the account by clicking my name (ComcastAmir) and then clicking "private message me".