How to get a prepaid plan for calls and 3G data on an unlocked iPhone 4 in the US

I’m currently travelling while working for ReignDesign, and my latest destination is the United States. I have an unlocked iPhone 4 (bought in Hong Kong). In Australia and New Zealand I was able to buy a Vodafone micro-sim, slip it into my phone, and have phone and 3G data service on a pre-paid basis. In the US, it’s not so simple, for starters:

  • Not all carriers are compatible with the GSM network used on the iPhone
  • Most people are on contract: prepaid is much rarer than in other countries. If you’re only in the US for a couple of weeks, a contract isn’t practical.
  • Most SIMs are regular size, not micro-SIMs

So, how did I get things working:

1. At an AT&T store, purchase a GoPhone prepaid SIM. This costs $15. Each day you use phone or SMS, costs $2, but you can make as many phone calls and SMS (even international SMS) within the day as you want. You may want to add an additional $20 credit at the store (see step 4).

2. Chop down the SIM into a micro-SIM. This is scarier than it sounds. I downloaded and printed a paper template from this page, then used scissors to trim down the SIM.

3. Insert your new micro-SIM into your iPhone (use a paperclip or pin to open the SIM slot). Verify you are able to make a call. The iPhone should show your balance.

4. To get 3G data, you need to subscribe to a data package. For $19.99 you can add 100MB of data. You can pay for this on the AT&T website (though this seems to require a US credit card, so borrow a friend’s, or do this at the AT&T store)

5. Your phone will still give an error message “Could Not Activate Cellular Data Network: You Are Not Subscribed to a Cellular Data Service” when trying to use data services. You need to change the APN settings, which Apple helpfully don’t provide a user interface for. To fix this, get on a Wifi network, go to the unlockit nz website, choose “Custom APN”, then “US – AT&T”, then install the profile.

And you’re done!

Let me know if you have any problems following these instructions! Note this will likely only work for unlocked, but unjailbroken phones.

Matt Mayer

Matt Mayer is a founder at ReignDesign. Matt is from the UK and was based in Shanghai for ten years. He is now living in Bangkok, Thailand.


  1. Hi Matt

    Thanks for posting this information.
    I was in the USA in January 2011 and couldn’t find a way to get my iPhone 4 on convenient prepay as we’d done in Canada which was very frustrating. I’m going back to the USA from New Zealand next month and will try your suggestions.

  2. Hi,

    I just bought an unlocked iPhone and are trying to use it in the US (I’m only going to be here for 1 week) with an ATT go phone plan. I installed your profile but I still cannot get data. I get an “cannot open page. Safari cannot open the page because it could not connect to the server”

    Do you know why this is? How can I double check that the phone I bought is actually unlocked?




  3. Hi Matt,

    A big thank you for this posting. You have made my day. I am in the same situation than Marilyn. I had no problems connecting in Canada only in the US. AT&T doesn’t want anybody on their data plan with a prepaid card. The only way i could get it was the postpaid plan. So, I am glad to report that your tip is working great. Thank you again… LCA

  4. I followed the instructions to get a different APN and it was working fine with my ATT pay as you go 10cents a minute; 20 cents a text and data. Then I bought a data plan 10MB for $5 and then my data stopped working though it must have worked at some time b/c they say I’m down to 280KB. Did something change recently about APN from unlockit working? Can’t follow the instructions to download the iphone configuration utility because they say to create a new configuration file (where?). Please help or tell me any ideas. I’ve turned it off, resynced, rebooted, etc.

  5. So even thought AT&T say that iPhones do not work on their GoPhone prepaid network, I assume this is a loophole “unofficial” way? and for some reason AT&T just dont want to advertise this?!

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