View the data consumption of the current month via pass.telekom.de Unfortunately, it doesn't work - Congstar is apparently still flying blind here, just like features like Visual Voicemail are missing. But maybe the Telekom subsidiary will make some improvements, the pure performance (telephony and data transmission) as well as the prices are ok.
Apparently, Telekom has the Speed manager or the possibility to influence it is deactivated - at least a corresponding message appears when you try to access the corresponding page with a Congstar-SIM.
In the age of LTE and similarly fast mobile data connections a service like Speedmanager is not really necessary anymore. But if you still want to compress data using Raspberry Pi, Privoxy & Ziproxy itself something similar to the Speed Manager together - even if this is not as easy as using the Speed Managers.