You'll need to run the UICC Unlock app inside system updates. I did this for my non-active Sprint V20 while connected to WiFi and it worked great. I was able to use an AT&T and T-Mobile SIM card in it without issue. APN settings come through in a kind-of text message. I wouldn't recommend doing tech support again. Under Settings should be System, System Updates, here will be UICC Unlock. This will tell you after a minute if Sprint domestically unlocked your phone. If it says your phone is locked to Sprint only, go chat with them online and reques.
Part 1: Free SIM Unlock Samsung Galaxy by Network Provider
Request an Unlock Code from Network Provider
After fulfilling the contract with the carrier, you can get a unique sim network unlock pin for Samsung Galaxy SIM unlock free from the carrier. The terms and requirements may differ from every network carrier. You can check your contract or go through the carrier's website first.
If you fulfill all the requirements and you tell them that you are going abroad and want to buy a local SIM at the destination, carriers will provide Samsung Galaxy SIM unlock code for sure. After you get the unlock code, you can follow the steps below to unlock your Samsung Galaxy for free.
Step 1. Insert New SIM
After getting the code for Samsung Galaxy SIM unlock free, turn off your Galaxy and remove old SIM and replace it with new SIM from another network.
Step 2. Turn Your Samsung Galaxy On
When your device builds a connection to the new network, it will ask for unlock code.
Step 3. Enter the Code Correctly
Be sure to enter the exact code. If the code is entered wrong for several times, it's the only carrier that can unlock the phone because the device will be locked automatically. After entering the correct code, you will successfully switch to the new network.