using iPhone from one service provider in another (legally unlocked)

Discussion in 'iPhone' started by mysorekid, Jul 1, 2012.

  1. mysorekid macrumors newbie

    Jul 1, 2012
    Hi Everyone,

    I am a new member here and had a question. I recently moved to US from Europe and had an iPhone4 there and got it unlocked while coming over here. when I checked with at&t to use their service (in pre-paid) they mentioned that I will not be able to use the 3G option on my iPhone and same with Sprint Telecom as well. can any one tell me more about it?

    Thanks & Regards,
  2. TheBama macrumors 6502


    Jun 20, 2010
    Birmingham, AL
    Usually is just depends on what bands your particular model was made for.

    If AT&T doesn't support it, try verizon
  3. Pirate515 macrumors member

    Oct 18, 2011
    Well, Sprint was sort of right on what they told you. Your iPhone 4 will not work on Sprint (or Verizon) at all, let alone not be able to use 3G.

    In Europe, most if not all of the carriers are GSM-based. Here in the US, there is another technology being used called CDMA. Out of the 4 "major" carriers, AT&T and T-Mobile use GSM while Verizon and Sprint use CDMA.

    When the very first iPhone was introduced, it was a GSM-only handset. Same with for 3G, 3GS and 4. Given that at that time AT&T was the "exclusive" iPhone carrier here in the US, GSM-only version was enough for Apple as it worked with AT&T as well as multitude of carriers in EU and around the world. And when iPhone 4 was introduced in June 2010, it was originally a GSM-only handset like its predecessors.

    However, some time at the beginning of 2011 AT&T lost its exclusivity on iPhone when Apple started offering iPhone 4 to Verizon users as well. Although it looks and functions as the GSM iPhone 4, it has a different radio that supports CDMA only. So you can't take GSM iPhone to CDMA network and vice versa; and if you wanted to switch between these two kind of carriers, you had to buy a new phone.

    While the latest iPhone model (4S) has a hybrid GSM/CDMA radio inside and technically the same unit is capable of working on either kind of network, taking it between networks is not as easy as you think. If you have one from Verizon or Sprint, they will unlock the GSM portion so that you can use it with SIM from any foreign carrier, while here it will still not accept a SIM from any US-based carrier such as AT&T or T-Mobile. And if you buy a factory-unlocked 4S, you are only free to switch it between GSM-based carriers, Verizon and Sprint won't activate it.

    Now, let's go back to your situation. Given that you come from Europe, you most likely have a GSM iPhone 4. It won't work on Sprint or Verizon, but I do not see a problem with AT&T. AT&T might use different frequencies for their services than whatever European carrier you used to use it with, but as far as I know, all GSM iPhone 4 units were created equal and support a wide range of GSM, HSDPA and HSPA frequencies worldwide, so as long as it is unlocked and accepts AT&T SIM, you should be good to go. Maybe the issue is that AT&T does not allow pre-paid customers to connect at 3G speed and limits them to EDGE instead? Also, have you tried signing up for a post-paid plan? You may have a problem with that since post-paid plans come with a subsidized phone and a contract, phone companies check your credit before signing you up for one. Given that you are new to the US, you probably don't have any credit history here. However, in your case, you already have a phone and do not want another one, and therefore don't need a contract.

    Besides AT&T, another possibility to look into here would be T-Mobile. Although right now they use a different frequency for their 3G service, they are finally serious about winning over iPhone users and are in the process of re-farming their spectrum to run 3G over those frequencies supported by iPhone. They claim that they should be done by the end of the year, so even though you will be limited to EDGE on T-Mobile now, hopefully you'd be able to utilize 3G soon.

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