Cal. Public Utilities Code § 728

Whenever the commission, after a hearing, finds that the rates or classifications, demanded, observed, charged, or collected by any public utility for or in connection with any service, product, or commodity, or the rules, practices, or contracts affecting such rates or classifications are insufficient, unlawful, unjust, unreasonable, discriminatory, or preferential, the commission shall determine and fix, by order, the just, reasonable, or sufficient rates, classifications, rules, practices, or contracts to be thereafter observed and in force. In determining and fixing rates for a telephone corporation pursuant to this section or pursuant to Section 455, or in determining whether or not a proposed rate increase is justified pursuant to Section 454, the commission shall, among other things, take into consideration any evidence offered concerning the quality of the particular telephone corporation’s services as compared with that of telephone corporations in adjacent territory, and the permissible rates for comparable service charged by telephone corporations in adjacent territory.