Here's how I do mine. Assuming you already have your Straight Talk SIM in and voice working.
1. Get on wifi and goto unlockit.co.nz install the profile. At this point everything should work except for MMS. You should be able to send SMS to anyone, and pictures to anyone on iMessage, but not pictures (MMS) to anyone who doesn't use iMessage.
2. Go to Settings -> General. Pop your Straight Talk SIM out. You will get SIM not found and Cellular will grey out, there's no rush at this point.
3. Pop the T-mobile SIM in (this is where it will likely take a couple tries), on my phone a "new voicemail" notification pops up (don't know if that's everyone or just me) close it. Cellular will ungrey and become selectable in a couple seconds (here's where you have to be kind of fast), choose it and the next screen will have Cellular Data, Data Roaming, Personal Hotspot, and just below that (I have to scroll down), you'll see the button for Network Settings. Your goal is to eject the SIM while in the network settings, and it will freeze there. If you make it into the network settings, then go to step 4. What happens alot, is before you can get the SIM ejected, an Apple logo pops up and you get the "Activation Required Screen". If you get the activation screen, just pop the SIM back out, and wait a couple seconds, then slide the slider, press the home button, and you'll be back to the home screen with the icons and the "no SIM found" message. Sometimes from here I could go back into settings, and still get into network settings, but most of the time I had to start the process over. It's very glitchy, but once you get good at it, it's pretty easy. I noticed after a failed attempt, I would start to get the "Activation Required" screen much faster. Putting the Straight Talk SIM back in seemed to slow things down again.
4. Assuming you made it to network settings and froze it there by popping the T-mobile SIM out: Now put your Straight Talk SIM in, and calmly double click your home button (there's really no rush now) to switch to the Notes app and then back and forth to the Settings app until you see the APN fill in with att.mvno. Once that happens, you are ready to put your new settings in.
5. The settings I use (and stored in the Notes app, so i could flip back and forth and cut and paste) are as follows:
APN (both cellular data and MMS): att.mvno
MMS Proxy: proxy.mvno.tracfone.com:80
MMS Max Message Size: 1048576
MMS UA Prof URL: http://www.apple.com/mms/uaprof.rdf
6. Try sending an MMS. If it works, then I toggled Airplane Mode.
At this point mine works and retains settings until the next iOS upgrade. I hope this is typo free, and helps someone.
I have done the SIM-swap on an unlocked iPhone 4, and it seems to be working for sending picture messages!
But I would like to better understand what I did! I am on a Go Phone prepaid plan without a cellular data package. I understand that MMS use cellular data but not "billable cellular data." (Pls correct me if I'm wrong about any of this.) I only want to enable the ability to send picture messages, not to "steal" any data and not pay for it. It looks like I have to have Cellular Data turned on to get the picture messaging to work. And I note that my Cellular Network Data usage is now not 0 Kb.
I'll add the $5 monthly Data Package if I have to, but I just want to know if I need to do that. BTW I had picture messaging working on my 3Gs which apparently I wasn't supposed to have (?), and that was without Cellular Data. Just trying to learn.
Ok, I got my sim card today and then started looking as to how to change the APN settings. First I found this thread (thanks to Google), then I found the solution.
The sim-swap deal seemed rather kludgy for an Apple product, and all I had was the dead AT&T sim that came with the phone so that was no help anyway.
Then I found this - the iPhone Configuration Utility. Right here on Apple's support site. (This link takes you to the KB article, follow the links to download)
It's a little daunting but after a little trial and error, I managed to create a config profile that works great.
First thing is after your StraightTalk sim is active and you can make and receive calls, check to see if your texting and MMS is already working. Mine was, I guess since it was an ATT phone in the first place. If it is, you don't have to mess with it, all you need is the cellular data settings. If not, good luck. (I can't help ya there)
Download and install the utility. They have Mac and Windows versions available
Run it then hook up your iPhone
Click on Configuration Profiles
Click on the New button
You'll see a whole list of possible settings. First click on General.
Give it a name... I called mine WebAccess
Give it a unique ID. it has to be "com.blablablawhateverwhatever.profile" (Obviously, replace everything in the middle with whatever you want)
Give it a description. (mine? "Hopefully Grants Web Access")
Now scroll all the way down to APN and click on it
Click the Configure button that appears in the window on the right
You'll notice right away that there aren't enough fields to include everything they say you should.
The MMSC, MMS Proxy and MMS Port settings weren't needed anyway since MMS was already working.
Access Point Name (APN) - att.mvno
Access Point User Name - leave blank
Access Point Password - leave blank
Proxy Server and Port - proxy.mvno.tracfone.com : 80
Click on the Export button
Click on the dropdown and select the "Create and sign encrypted configuration profile for each device" option, make sure your iphone is connected and highlighted and hit export. You'll see an install window pop up on your phone, hit the install button. After it loads it on your phone it lets you save it to your computer as well. Name it anything and save.
Restart your iPhone. It should be online and good to go. IF you get stuck like I did, the help menu in the program will take you to the knowledge base online help for the utility. Very well done, answered my questions and got me going. This all looks like a lot but really, it only took about 10-15 minutes and that's with a couple shots in the dark.
Good luck! I hope this helps someone out there.
I tired the configuration utility but it just didn't work for me. I am using iPhone 5 iOS 6.0.1 and the sim-swap method worked. I had to play around with it a few times and then realized I needed to remove the unlockit.co profile and once I did it worked right away. No reboot but I did turn on Airplane Mode and held it for about 30 seconds. I am pleased and I am on H2O. Go figure! Thanks for the help and keeping my unlimited Data surging!
madman459: can you upload the APN that you have working to unlockit? Or can unlockit not install it to Straight Talk phones?
ALso -- Where is a source for these infamous T-Mobile sims that are apparently magic?
None of my friends use T-Mobile as they have no service here.
There's not T-mobile store so I can't go in and ask for an old junk one.
There is not a thing online I can find to order one.
Regretting upgrading to IOS6 as the benefits aren't there, siri didn't arrive on my iPhone 4, didn't get panoramic camera capability, and now my MMS is broken. >:(
If anyone out there on an iPhone4 using Straight Talk sees this - take my advice and wait.
I tried to downgrade my phone twice to get back to IOS 5.0.1 and haven't been able to.
I stopped at a T-mobile store and got one while traveling, there's not really any T-mobile here either. I got it for $10. The SIM swap tricks not hard once you've done it a couple times, but honestly when I upgrade to the iPhone 5, I won't bother because most everyone I ever send an MMS to (rarely), is on iMessage now. It's not even worth the 2 minutes it takes me to do it.
I personally am on iOS6 for my iPhone 4S. The sim swap works for me temporarily. I do the swap, update the info, stay on the page, make sure it doesnt revert, but then at some point after some days or maybe a week, I loose all the info and revert to no data or mms.
Has anyone experienced this at all?
Please let me know if you found a way to work thorugh it?