I bought what I thought was an unlocked 3GS that worked great with a prepaid tmoblile sim, but when I actually switched to tmobile & they tried to activate it, it locked. It had been jailbroken with Cydia (unknown when I bought it). I am a complete newbie when it comes to anything apple, but learned lots in last 3 days. My phone had 4.1 originaly & I wanted to update it anyway, so I paid to have it unlocked but when it didn't work, I had collaborated with the guy who tried to unlock it. He told me it was probably jailbroken and he finaly figured out it must have an ipad baseband. Because he unlocked it over the internet, he told me where to find you. So I downloaded the iphone 6.0.0 software or firmware that he told me to and redsn0w ver 0.9.15b3 and did it myself. Well everything was great, itunes told me my phone was unlocked, yeah! but now it won't ring. So when I checked the APN settings, they weren't right, they said fast.t-mobile.com instead of epc.tmobile.com, there was no MMS Proxy or MMS UA Prof URL. Changed those, still wont ring. Did I download the right files? Well I'm up to date, now I have version 6.1.3 and firmware 05.16.08. And the sound works great for everything but calls, what do I do? Thanks.