Service Providers shall not transfer or attempt to transfer customers, and shall not charge customers for services except in accordance with customer orders, agreed service terms or other written customer directions. In addition to the orders issued by the General Secretariat regarding customer terms, service provision or billing, service providers shall provide customers with invoices:   1.      At least once every three (3) months and for free. 2.      In paper form, or in electronic form if the customer consents. 3.      In a plain and simple format. 4.      With accurate information about the services provided, the amounts due for each service, and the method of calculation of tariffs for any service, such as the length of calls or other measure of usage, on which invoices are based.   Article 88 Service providers shall retain accurate records of all customer orders, service provisioning and billing for a period of at least twelve (12) months from the relevant billing date, and shall make them available to the General Secretariat upon request in accordance with the Law.   Article 89 Where the General Secretariat has a concern relating to billing practices, it may require service providers to publish information on billing systems or billing practices or to take such other steps relating to their billing systems or billing practices as the General Secretariat may consider appropriate.   Article 90 1.      No service provider shall make any false or misleading claim or suggestion regarding the availability, price or quality of its telecommunications services or equipment, or regarding the telecommunications services or equipment of another service provider. 2.      A claim or suggestion is false or misleading where the service provider knew or ought to have known at the time it was made that it was false or misleading or that it was likely to deceive or mislead the person to whom it was made.