You can buy android tablets with a 10.1" screen that have an unlocked phone in them (ie takes a sim card) . So if you go online on these "phablets" are you charged data fees as if using a cell phone or as tethering (which I think is much more costly) ?
Long Answer: Tethering is considered when you use the "Hotspot" feature. However, with newer plans. Data and Tethering are no longer considered seperate. So you can tether or use data and it will count from the data allotment of the plan the sim card is associated to.
Additional Info: If this tablet makes calls, and your plan is just data pla (No minutes or text). Calls and SMS/MMS will be considered Pay per Use. If this tablet uses Data, and your plan is just voice/text plan (No data included). Usage, Data or Tether will be considered Pay per Use.