Used to be a thing with O2 here in the UK. My iPhone 3G (so, 2009?) was affected so I had to install an app that allowed me to tether.

Apart from SMS Auth and occasionally a "NEW FIRE BUD 10/10 stardawg smoke ring me" messages, apart from those SMS is dead..

You're right on the money with this comment, what a strange country they have over there..

think of it more like a switch that makes that part of your keyboard multi-use.

You can buy keyboards that cut off that entire section if you don't use it.