Archive for March, 2016

How to activate an old, 15-digit SIM card on T-Mobile

March 14, 2016

I have thought about blogging my ordeal trying to unlock a Sprint iPhone 4s on T-Mobile, and I may well do that. But right now, since I have yet to successfully get this out-of-contract, paid-for phone off its software-tethered carrier, I need to deactivate the teeny-tiny SIM card I got for the iPhone, and reactivate the same old SIM I was using in my Android phone, the same one I’ve had for 10 years, so I have some phone to use.

When I called customer support, however, I was told it couldn’t be done. I asked if they had a way to look up my SIM cards and just use whatever they showed the previous one to be; I was asked for the number so they could look it up. (It’s still unclear whether they have access to those records; I assume not.) I wasn’t sure which number they were asking for, since there is one printed horizontally and one vertically, but assumed the 6-digit code was too short to be any kind of unique identifier. So I read off the other number that was printed. “I’m sorry, sir, the system won’t let me activate a card with fewer than 19 digits.” The SIM card I had had three groups of four digits and one group of three at the end. Searching for images of T-Mobile SIMs, I saw three groups of five digits followed by one group of four. “Well, then put four 0s in front of it,” I suggested. “If that doesn’t work, put four trailing zeroes.” Still no luck. The computer wouldn’t accept it. “That’s ridiculous!” I screamed in protest. “This card was working just a week ago! If it worked then, there has to be some way to make it work now!” I even bugged the poor kid till he put his manager on. No dice, I was told. Finally, I hung up in defeat. I vowed to call again in the morning and harass their American customer support, who of course would be able to connect me to a tech who actually knew what they were doing.

However, after I mulled over “the code will start with 8901,” for a few moments, looking at those pictures online, a lightbulb went off. I called back and said I wanted to reactive my old SIM card. “No problem, sir,” I was told. “Could you please give me the number off the back of the card?” “89012…” I read off. The old 15-digit code starts with a 2, so I just read off the following digits in groups of five, followed by the last four digits. “OK, sir, that SIM card has been activated. Is there anything else we can help you with today?”

TL;DR: To use an old T-Mobile SIM, just give them the old number prefixed with 8901, giving you a total of a 19-digit code.

I can’t lie, I kind of feel like a bad-ass hacker right now.