Hey guys,
So I think I may have found a way around the issue for people on Three. I have a rooted S7 so not 100% sure if this will work on stock phones but I dont see why not. Simple steps ...
1. Settings > Access Point Names
2. I use the default access point with the name "3" not "3 Hotspot"
3. Go to edit the point and scroll down to "APN type'
4. Just add ",dun" to the end and hit ok - (so for example will look like "default,supl,mms,dun")
5. Reboot phone and you should now have unlimited tethering!
Just as a note, the first time I tried this on the rooted device I used an app called "ISWAT Tether Unblocker" first then went on to step 2 above. Doubt that it would have changed much as I have flashed other roms and just followed the above steps without the app. I have been tethering laptops and tablets with no problem
Hope this works for you!