California Code, Public Utilities Code - PUC § 2890.2

(a) A provider of mobile telephony services, as defined in Section 224.4, shall provide subscribers with a means by which a subscriber can obtain reasonably current and available information, as determined by the provider, on the subscriber's calling plan or plans and service usage, including roaming usage and charges.

(b) On or before January 1, 2007, a provider of mobile telephony services shall provide subscribers with a means by which a subscriber can obtain reasonably current and available information, as determined by the provider, on the subscriber's text messaging and Internet usage and charges.

(c) Each provider of mobile telephony services shall inform subscribers at the time service is established of the availability of the information described in subdivisions (a) and (b) and how it may be obtained.