Do switching costs reduce or intensify price competition if firms charge the same price to existing and new consumers? I study 800-number portability to determine how switching costs affect price competition under a single price regime. AT&T and MCI reduced their toll-free services prices in response to portability, implying that reduced switching costs increased competition. Despite rapid market growth, gains from higher prices to “locked-in” consumers exceeded the incentives to capture new consumers. Prices on larger contracts dropped more, consistent with greater lock-in for larger users. Price changes between portability's announcement and implementation are consistent with rational expectations.