I am also asking my Mercedes dealer about this. According to him, it is a subscription offered by Mercedes that you sign up for with your mobile phone operator. Normally, when you connect your phone to the MBUX via Wi-Fi and launch your web browser, a page should appear showing the subscription terms and conditions. He also told me to check the Mercedes app on your phone to see the services offered, and I found this. I'm still looking into it.
"How can I activate my digital offers?
1. Ensure that your vehicle is in an area covered by a network connection. This is a prerequisite for activating or deactivating your connected services.
2. Log in to the Mercedes-Benz app.
3. Open the ‘Garage’ via the ‘Car’ button at the top left of the app.
4. Select your vehicle.
5. Tap ‘Manage connected services’ to open the list of all connected service categories available for your vehicle.
6. Select the service category for which you wish to activate the connected service. Next to each connected service, there is a slider button that allows you to activate it. The greyed-out slider button corresponds to connected services that have not yet been activated, and the blue slider button corresponds to activated connected services.
7. Once a connected service has been activated, the new setting is sent to your vehicle. Please drive your vehicle outside for a short time to ensure that it receives the activation signals. It then takes approximately 30 minutes for the connected service to be fully activated"