Case C-539/19: Judgment of the Court (Eighth Chamber) of 3 September 2020 (request for a preliminary ruling from the Landgericht München I — Germany) — Bundesverband der Verbraucherzentralen und Verbraucherverbände — Verbraucherzentrale Bundesverband eV v Telefónica Germany GmbH & Co. OHG (Reference for a preliminary ruling — Roaming on public mobile communications networks within the European Union — Regulation (EU) No 531/2012 — Article 6a — Article 6e(3) — Roaming provider required to automatically apply the regulated roaming tariff — Application to consumer having opted for a specific roaming tariff prior to the entry into force of Regulation (EU) No 531/2012)