15 Article 24 Public telecommunications operators take the measures set out in this Article to ensure that personal information relating to an individual user of telecommunications services and telecommunications networks is protected. Public telecommunications operators may process data which is strictly necessary for providing bills to users and for determining interconnection payments. Processing is permissible only up to the end of the period during which a bill may lawfully be challenged or payment may be pursued through legal means. Traffic data relating to users which is processed to establish and charge for calls and which has been stored by public telecommunications operators will, subject to paragraph 2 of this Article, be erased or rendered anonymous at the end of each call. Processing of traffic and billing data is restricted to: 1° natural persons who are employed by public telecommunications operator or; 2° natural persons or organizations who are under contract or with the public telecommunications operator. In such case, any data disclosed are strictly limited to that data which is necessary to enable that person or organization to carry out its contract with the public telecommunications operator. This Article does not prejudice the right of the Regulatory Board to be supplied with such information as it requires pursuant to law. On written request to the public telecommunications operator, a user is entitled to have a nonitemized bill. The Regulatory Board has the power to lay down rules about the limits of itemization which users may request and the conditions on which these may be provided. Article 25 The public telecommunications operator can not use any personal, call traffic or billing data about a user when marketing its services without the explicit written permission of that user. In the case of contravention of paragraph (1) of this Article, users in the first instance request the public telecommunications operator to cease using their personal details for marketing purposes. In cases of continued contravention, the user may notify the Regulatory Board, which issues a notice prohibiting the public telecommunications operator from using the user’s personal details and may order the operator to pay compensation to the user as the Board determines. Article 26 It is forbidden for any natural person or organization: 1° to use any automatic calling machine, facsimile machine or any other device of the same kind;