After that, they degrade services that are not paying them and zero-rate + allow higher bitrates for services that pay them. "degrade services that are not pay

After that, they degrade services that are not paying them and zero-rate + allow higher bitrates for services that pay them. "degrade services that are not paying them" and "allow higher bitrates for services that pay them" would even more blatantly violate FCC net neutrality in the US. T-Mobile here is circumventing this by only zero-rating with an opt-out mechanism. If they tried to pull a stunt like Deutsche Telekom in Germany, they'd be fined in no time by the FCC in a clear and shut case. They are doing something far more subtle here in the US. EDIT: For clarity, Deutsche Telekom is a majority shareholder of T-Mobile USA.