@ptonks wrote:How do I prevent this in the future?
You make sure that nobody else ever gets physical access the SIM card or its unique SIM ID number (along with relevant personal and account-related information).
For maximum security, only buy SIM cards directly from the source: Public Mobile itself. Not from retailers. Not from online vendors. Certainly not from ebay or craigslist. The idea is to minimize any chance of other people copying the unique SIM card number.
Don't leave your phone in places where others can access it without your knowledge (like on a charger at work or school, etc). Don't lend it to people you don't know and trust. Even if you lend it to people you trust, understand that you may not trust everybody they trust in turn.
I go so far as to scrub off the number printed on the SIM card. And, of course, I always screenlock my phone with a PIN/passcode key which I don't share (and change anytime I suspect it might have been observed or compromised be people I don't trust) - and I use any additional security codes or layers the software has built in, so (without PIN/passcode key) settings can't be changed and contacts can't be edited and device data (like the IMEI and SIM ID) can't be seen.
Most victims of SIM jacking are those who purchased too-good-to-be-true cheap SIM cards and/or who allowed others to setup everything for them instead of doing it themselves. You shouldn't have to submit any personal information (beyond perhaps your phone number and your provided email address) to anyone other than Public Mobile itself. You should be wary if retailers/vendors entice you with an extra $10 or $20 because it typically means they're using you as a referral - which means their professional ethics (along with the opinions of their customers and of Public Mobile) are already questionable.
Once a SIM card has been compromised it can be hijacked (a technical form of identity theft/fraud). Most criminals will probably strike as soon as they can. But they could wait indefinitely, a compromised SIM card will remain vulnerable as long as you keep using it, possibly for many years and across multiple devices. It's just a risk or a problem which I don't personally think is worth buying, especially since "full" price is just ten bucks.
