12) data on the quality of service, in particular the minimum service quality levels offered, including the time for the initial connection and other quality of service parameters, if defined by the President of UKE under Article 63 (2a); 13) ways of informing the subscriber about exhaustion of its data transmission package in the case of the Internet access service provided over the public mobile telecommunications network and about the possibility to monitor the package usage level by the subscriber; 14) the scope of maintenance service and means of contacting the entities offering these services; 15) the scope of liability for non-performance or improper performance of an agreement, the level of compensation as well as the principles and time limits for its payment, in particular if contracted service quality levels are not met; 16) the principles, procedure and time limits for filing and considering complaints; 17) information on proceedings related to out-of-court consumer dispute resolution and proceedings before permanent consumer arbitration courts by the President of UKE; 18) the method of obtaining information on up-to-date tariffs and the costs of maintenance services; 19) the principles of including subscriber's data in a directory in the case of agreements for the provision of voice services; 20) ways to provide information to the subscriber about any risks related to the service provided, including on the ways to protect security, privacy and personal data; 21) any charges due on termination of the contract, including the terms and conditions for returning telecommunications terminal equipment, indicating at whose cost this is to take place. 4. An agreement for the provision of connection to a public telecommunications network apart from the elements referred to in paragraph 3 should define the number assigned to a subscriber and, in the case of connection to a public fixed telecommunications network, also an address of a network termination point. 4a. In the case of a consumer an initial validity period as specified in an agreement referred to in paragraph 1 concluded with a specific service provider shall not exceed 24 months. 4b. The service provider shall ensure that the end user has the possibility to conclude an agreement for the provision of telecommunications services also for a period not longer than 12 months. 5. The data referred to in paragraph 3 point 6-8 and 10-21, based on an explicit provision of an agreement, may be included in the rules and regulations for the provision of publicly available telecommunications services. 6. A service provider may enable its subscriber as a party to an agreement concluded in a written or electronic form to modify the agreement terms and conditions referred to in paragraph 3 point 2, and points 4-7 by remote means of communications, in particular via a telephone or using electronic mail or fax. The service provider shall be, however, obliged to record the subscriber's statement made in the manner specified in the first sentence and to store it until the end of the validity period of an agreement under modified terms and conditions as well as to make available its content to the subscriber at its every request submitted in particular in the course of a complaint procedure. In the case of modifications to the agreement terms and conditions made by means of a telephone, the whole conversation should be recorded. At the same time, the service provider shall be obliged to confirm the statement on modification to agreement conditions as well as its scope and the time limit for effecting the modifications made by the subscriber, within the time limit agreed with the subscriber, but not later than within one month of a request for modifications. The subscriber shall be entitled to withdraw from modifications made to the agreement, without stating the