I can't seem to switch the Scarlet website to English

If you are in the process of placing an order or if you are on the login page of mon.scarlet, it is not possible to change the language directly. The language of the page is the language configured in the settings of your web browser (Internet Explorer, Safari, Chrome, Mozilla Firefox,...).

If the page is displayed in Dutch, it means that your web browser is not configured in English.
To display the page in English, simply open your browser settings to change the language.

As far as your mon.scarlet customer zone is concerned, it is displayed in the language you registered when you placed your order.