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I have an officially unlocked iPhone 4 from a non-US carrier. Now that I'm in US, if buy a prepaid SIM card from AT&T and use it in iPhone, do I get 3G(WCDMA) or GSM network? To put it in the context, do I see "3G" or "E" in the iPhone status bar?

Could anyone clarify if this chart is correct?

Enable 3G, Enable Cellular Data, Result
Yes      , No                  , Make 3G call;  use no data
Yes      , Yes                 , Make 3G call;  use 3G data
No       , Yes                 , Make GSM call; use EDGE/GPRS data; 
No       , No                  , Make GSM call; use no data; 
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I don't know the answer but wanted to point out that E is EDGE service and O is "GSM" service. – Aaron Nov 10 '11 at 3:57
up vote 0 down vote accepted

Presuming that it's not a CMDA iPhone (i.e. not from Verizon/Sprint), you will see '3G' if you're in a 3G coverage area. The Enable 3G and Cellular Data options must be turned on in the Settings.

Sidenote: AT&T requires purchasing a data package for their smartphones; no Pay per use.

As AT&T also had a GSM network, you could also access that (and GPRS/EDGE as well).

Usual Terms and Conditions will probably apply.

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Hi, I updated the question, could you take a look? Thanks! – Wei Shi Nov 10 '11 at 14:58
Yes. That chart is correct. Assuming you are in a coverage area with both 2G and 3G. If you were using Bell or Telus' network in Canada, they don't have GMS or GPRS/EDGE so you would lose all service if you disabled 3G. – mockman Nov 11 '11 at 3:28

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