3. National regulatory authorities and, where applicable, other competent authorities shall, in accordance with their respective competences, in preparation for the review provided for in Article 21, monitor developments in wholesale and retail charges for the provision to roaming customers of voice and data communications services, including SMS and MMS, including in the outermost regions referred to in Article 349 of the Treaty on the Functioning of the European Union. National regulatory authorities and, where applicable, other competent authorities shall also be alert to the particular case of inadvertent roaming in the border regions of neighbouring Member States and monitor whether traffic-steering techniques are used to the disadvantage of customers.
National regulatory authorities and, where applicable, other competent authorities shall monitor and collect information on inadvertent roaming and take appropriate measures.