4. The national regulatory authority and, where applicable for the exercise of the powers conferred on them by national law transposing Directive (EU) 2018/1972, other competent authorities shall strictly monitor and supervise the application of fair use policies. The national regulatory authority shall strictly monitor and supervise the application of the measures on the sustainability of the provision of retail roaming services at domestic prices, taking utmost account of relevant objective factors specific to the Member State concerned and of relevant objective variations between roaming providers. Without prejudice to the procedure set out in Article 6(3), the national regulatory authority shall, in a timely manner, enforce the requirements of Articles 5 and 6 and the implementing acts provided for in paragraph 2 of this Article. The national regulatory authority may at any time require the roaming provider to amend or discontinue the surcharge if it does not comply with Article 5 or 6.
Other competent authorities shall enforce the requirements of Article 5 and of the implementing acts which are relevant for the exercise of the powers conferred on them by national law transposing Directive (EU) 2018/1972, as the case may be.
The national regulatory authority and, where applicable, other competent authorities shall inform the Commission annually concerning the application of Articles 5 and 6, and of this Article.