There is some confusion here.
Internet sharing is not a network feature. ATT and others can not turn it off in the network as you are sharing the same data access as you use for browsing in the phone so instead that have implemented an app that works a bit different depending on OS. In the case of an ATT Lumia 920 phone it has the ATT specific firmware with an app that checks against ATT servers if you have thefeature on your plan.
In Nokias case I do not believe the unbranded version of the phone has this app that check against servers you can just turn it on... (Like in any unbranded none ATT phone for the past 7 years)
Apple has the worst implementation where they disable hot spot when you put in an ATT compatible SIM even on a full priced unlocked device!!. I wonder if this is really legal.
However, Jailbreak apps like tetherme restores this native functionality in the iPhone and it works very well regardless of plan or carrier. (I am using Straight Talk)
In most countries this is enabled and you are able to use your data anyway you like. Not sure what ATT does to get away with this but Verizon was fined here in the US. http://news.cnet.com/8301-13578_3-57484000-38/verizon-to-pay-$1.25m-fcc-fine-forced-to-allow-tethering-apps/
Internet sharing is not a network feature. ATT and others can not turn it off in the network as you are sharing the same data access as you use for browsing in the phone so instead that have implemented an app that works a bit different depending on OS. In the case of an ATT Lumia 920 phone it has the ATT specific firmware with an app that checks against ATT servers if you have thefeature on your plan.
In Nokias case I do not believe the unbranded version of the phone has this app that check against servers you can just turn it on... (Like in any unbranded none ATT phone for the past 7 years)
Apple has the worst implementation where they disable hot spot when you put in an ATT compatible SIM even on a full priced unlocked device!!. I wonder if this is really legal.
However, Jailbreak apps like tetherme restores this native functionality in the iPhone and it works very well regardless of plan or carrier. (I am using Straight Talk)
In most countries this is enabled and you are able to use your data anyway you like. Not sure what ATT does to get away with this but Verizon was fined here in the US. http://news.cnet.com/8301-13578_3-57484000-38/verizon-to-pay-$1.25m-fcc-fine-forced-to-allow-tethering-apps/