People with a cellular plan that works for them tend to stick with it for a while, according to a new report from Consumer Intelligence Research Partners (via Business Insider). But for AT&T at least, no plan is proving as sticky as unlimited data. 44% of AT&T customers are on grandfathered unlimited plans — that haven’t been offered since 2010. The report uses data from a survey of 500 people, and it estimates what proportion of subscribers to the big four carriers are on unlimited data plans. CISP’s survey, however, contradicts AT&T’s own numbers which state that “81% of smartphones are on metered plans.” Aside from AT&T, of course, Sprint and T-Mobile, both of which highlight unlimited data in their marketing, have 78% of their customers on unlimited plans.