How to let Comcast know about a complaint regarding a Comcast Branded Partner store

I've been to a Xfinity Comcast Branded Partner Store (didn't realize it was a Partner Store until doing research after the problems) twice within the last 6 months and had serious problems both times. One of the problems was resolved by calling Comcast, the other couldn't be completely resolved. The store changed me from a grandfathered plan to a new plan resulting in a $95 monthly increase without my knowledge. Much time spent on the phone and no one could revert me to the old plan. I got my bill down by cancelling Home Security and by removing a $40 landline fee that was added to my account by the store without my knowledge. When I went to Google Map reviews to give the store 1 star, I noticed another report about the first problem I had and another report about the $40 landline being added. There may have been other reports as I didn't go through all of the reviews -- but 2 reports about a landline being added to accounts makes me suspicious. I don't need any more help on these issues but I would like to know how to notify Comcast about this store.