Consumers may overestimate the precision of their demand forecasts. This overconfidence creates an incentive for both monopolists and competitive firms to offer tariffs with included quantities at zero marginal cost, followed by steep marginal charges. This matches observed cellular phone service pricing plans in the United States and elsewhere. An alternative explanation with common priors can be ruled out in favor of overconfidence based on observed customer usage patterns for a major US cellular phone service provider. The model can be reinterpreted to explain the use of flat rates and late fees in rental markets, and teaser rates on loans. Nevertheless, firms may benefit from consumers losing their overconfidence.

Following FCC pressure to end bill shock, cellular carriers now alert customers when they exceed usage allowances. We estimate a model of plan choice, usage, and learning using a 2002–2004 panel of cellular bills. Accounting for firm price adjustment, we predict that implementing alerts in 2002–2004 would have lowered average annual consumer welfare by $33. We show that consumers are inattentive to past usage, meaning that bill-shock alerts are informative. Additionally, our estimates imply that consumers are overconfident, underestimating the variance of future calling. Overconfidence costs consumers $76 annually at 2002–2004 prices. Absent overconfidence, alerts would have little to no effect.

At‐scale field experiments at major U.K. banks show that automatic enrollment into “just‐in‐time” text alerts reduces unarranged overdraft and unpaid item charges 17% to 19% and arranged overdraft charges 4% to 8%, implying annual market‐wide savings of £170 million to £240 million. Incremental benefits from “early‐warning” alerts are statistically insignificant, although economically significant effects are not ruled out. Prior to the experiments, over half of overdrafts could have been avoided by using lower‐cost liquidity available in savings and credit card accounts. Alerts help consumers achieve less than half of these potential savings.