Very good, you have just made my day. I am owning a Lumia 1020, produced and branded by ATT, unlocked and otherwise working since July 2013. And now I was facing an urgent need for getting tethering to work.
Had some 5 or 6 phone calls with T-Mobile and ATT first and second level support today. ATT did ultimately state that this is exclusively a T-Mobile issue. And T-Mobile technical support had nothing better than advising me to organize a Windows Phone developer license for a fee they said would be around $100 and then find my way towards unlocking everything and all on 1 smartphone of my choosing, warning about technical challenges. Told them that I am already part of the free MS frequent phone software update program for developers and get the latest pieces automatically applied - they insisted that this would not be the same.
After a successful application of your guideline I suggest 2 changes/additions in your great script:
- For the date setting under part II, the functioning range seems to be rather constrained. On my first attempt I did quickly key in something around the year 2070. Instead of suggesting a deinstallation I got the AP software complaining about missing SIM chip. A second go with a date around 2150 brought other issues. My third attempt with current month and day in 2113 did ultimately work. Save the reader some stress by leaving out “(or something ridiculous)”.
- You can add “Vodafone Germany prepaid” for SIMs that did do the trick.
PS: the unlocking seems to be permanent and independent from the specific T-Mobile subscription SIM. Could immediately use a different T-Mobile SIM chip and get it working as well without any extra action at all.
Thanks again,
Stefan