Samsung Galaxy S3 SCH-I535, rooted, won't switch over to T-Mobile Recently, I changed carriers from Verizon to T-Mobile. However, when I inserted my T-Mobile SIM card into my phone and rebooted, the status is always "Searching for Service" (not just for data, NOTHING works). I've looked on Android forums and they all have instructions for turning the SCH-I535 into a world phone, but that's not what I want. I just want to switch to T-Mobile (do I need to have a "world phone" to do this?)

I've installed APN Manager and tried to change APNs, but entering the details found here

The phone is rooted and not on a stock TouchWiz ROM (I'm using Paranoid Android, a JB ROM)

Why won't my phone recognize the T-Mobile SIM?
SCH-I535 is not a GSM phone so will not work with any 2G or 3G T-Mobile tower. Also that phone only supports LTE frequencies of 700 MHz &amp; 1900 MHz, neither of which are bands that T-Mobile use to any significant degree. Instead T-Mobile uses 1700 &amp; 2100 MHz. 

T-Mobile is however in the process of rolling out 700 MHz &amp; 1900 MHz, so you might get data in the near future however you will not generally be able to make calls as that is currently handled by the 3G networks. And even where VoLTE is available this phone will may not have the software update to support it.

Update: Despite not being listed in the specs of Samsung's website, nor GSM Area, or Wikipedia SCH-I535 does infact support GSM beyond LTE. It appears that Verizon pushed out an update with 4.1.2 Jelly Bean which enabled support for GPRS/EDGE/GSM 850/900/1800/1900 MHz and HSPA/UMTS 2100 MHz (band 1). T-Mobiles 3G support requires AWS-1700/2100 (band 4), however they do support 1900 MHz for GSM/EDGE 2G service.

So you can get EDGE but not HSPA, although you may soon get LTE depending on T-Mobiles rollout.