This app from the Google Play Store worked for me. I emailed the developer with my question, and he got back to me promptly, stating that his app should work on the S3 and he would refund my purchase or provide support if it did not. You can't get any better than that!
Wifi Tether Router
The app costs $2.50
Here's the problem I encountered and some of the other solutions that I tried:
I have a Freedompop Galaxy S3 phone. I bought it because the Freedompop representative in a woot.com product forum stated that the Galaxy S3 phone would allow wifi tethering. The Freedompop FAQ pages also stated that the Galaxy S3 phone would allow wifi tethering. Freedompop uses the Sprint network.
(Bad, FreedomPop, bad. Here's the response that I received from their rep, which was not what they promised when I bought the phone! :
I believe that Freedompop needed to contact Sprint and ask them to allow this phone to allow wifi tethering. Good luck with that. FreedomPop's customer service is not exactly helpful.
I researched this issue for several hours and learned that this phone has Android 4.4.2 KitKat, which has some kind of hidden "KNOX" software that does not allow any normally-used wifi tethering apps to work.
I have used Root Check, and it seems that the phone is rooted. I have tried to remove the KNOX software using Terminal Emulator but I don't believe that did anything. I've tried wifi-tether-Trevemod also which did not work and told me that there were errors and I should look at the log file -- then told me that the log file did not exist. It seems that the app wifi-tether-Trevemod only works with phones up to Android 4.3.
I also tried Foxfi and PDANet. The phone did allow USB tethering using PDANet.
With all the above wifi tethering apps (FreedomPop, Foxfi, TreveMod), here's what happened:
Under Settings-Connection, when I attempt to enable "FreedomPop hotspot"; I get the following error messages:
“hotspot error --
you are not subscribed to the hotspot service, do you want to see subscription options?
Cancel or OK.
Selecting OK gets:
"Welcome to self service" (grayed out). Then:
Self Service: Information: sorry experienced a system problem during your task, please dial *2 from your Sprint phone or call custom care at 888-211-4727 from another phone to complete your task”
I tried calling Sprint customer service, and the agent told me that they could not help -- that FreedomPop had to set the phone up properly (provision it).
Before using the Wifi Tether Router app that works, you need to be sure that your phone is rooted. My phone came rooted already. Use the free app "Root Checker" to see if your phone is rooted. I would not advise trying to "root" your phone if it is not already rooted. Rooting your phone will void any warranty.
(Update: on a new phone, I installed Root Checker, which told me that my phone was not rooted. I then used SuperSU to root my phone. It hung up on the message "disabling Knox" which is something you DO want it to do. After checking forums, I found that this is a common problem. Just restart your phone and you should now have rooted your phone. The Wifi Tether Router App should now work.)