If I move from AT&T to another service, will it effect SEO?

Trying to help my dad with this. He wants to move the phone and internet plan for his business to something besides AT&T, because they have very poor service. They warned him if he did so his SEO would be negatively effected, as they have his business on some sort of internal list that search engines use. Is this true? Will there be any noticeable hit to his presence on search engines?