AT&T didn't just buy into a significant amount of DirecTV, they owned DirecTV. As in, 100% ownership. So yes, all DirecTV customers were AT&T customers, because

AT&T didn't just buy into a significant amount of DirecTV, they owned DirecTV. As in, 100% ownership. So yes, all DirecTV customers were AT&T customers, because AT&T and DirecTV were not separate entities. It wasn't until 2021 that DirecTV was spun off into a separate company again, but still with 70% ownership by AT&T.