No this is like buying Photoshop and Adobe saying you can't let your friend come over and use it without paying for a new license.

I paid for the data. There is no difference if I use the data request comes from my mobile device or if it comes from my laptop connected to my mobile device.

Price discrimination is not a god given right nor is it criminal (usually) to avoid. (I can't think of a case where avoiding price discrimination is criminal, but I'm sure there is)