[…] Member States may allow operators to require a payment from subscribers wishing to ensure that their particulars are not entered in a directory, provided that the sum involved does not act as a disincentive to the exercise of this right, and that, taking account of the quality requirements of the public directory in the light of the universal service, it is limited to the actual costs incurred by the operator for the adaptation and updating of the list of subscribers not to be included in the public directory.