Why doesn't the unlocked iPhone 4S work with Sprint or Verizon?

I'm clarifying to the folks who posted implying the SIM had any bearing on what the radio capabilities were.

But I'm sorry, I forgot that the point of these forums is for folks like yourself to practics being huge *********.

Just to clarify Apple is the only one that can actually unlock the phone, they usually do it once the carrier has sent them the request along with the phone's IMEI. The firmware is different for Verizon and Sprint devices, it’s preloaded with Verizon’s or Sprint’s MMSS file which can’t be updated over the air on the 4S The MMSS file is one of the things that tells the device to prefer CDMA over GSM when it goes through network acquisition

To use an AT&T 4S on Verizon and Sprint five things would need to happen.

1. AT&T would need to authorize Apple to unlock the device
2. Apple would need to unlock the device
3. Apple would need to load Sprint or Verizon’s MMSS file (there are a few other things as well)
4. Sprint or Verizon (depending on who you choose) would need to load the MEID of the device into their network
5. Sprint or Verizon would need to turn off SSD authentication once they’ve provisioned it for use

The biggest barriers to this are #3 and #5. Apple also doesn’t want to give carriers the software to flash and load firmware to their devices. (understandable). This leaves us with #5; CDMA networks have two authentication measures the first is by ESN/MEID and MDN, the second is SSD. In order for SSD authentication to happen the carrier needs know the secret key that is unique to your device, and they can only get this from the manufacture (in this case Apple) They can turn this level of authentication off for a customer, but it opens that customer up to device cloning fraud. So you can see why they don’t like to do that.

I would also add that the firmware load for Verizon and Sprint’s iPhones restricts SIM’s with US IMSI range (other than their own of course) from being used in the device. As mentioned above there is no way for Sprint or Verizon to change this on devices already produced. (Apple would have to re-flash the device)

You missed the part where the guts of the phone would have to be replaced so that it contained an active CDMA radio.

KiltedTim wrote:

You missed the part where the guts of the phone would have to be replaced so that it contained an active CDMA radio.

This has been stated many times and apparently needs repeating; the iPhone 4S is a dual mode phone! It has both a CDMA radio AND GSM/UTMS radio. My Sprint 4S works fine in Canada on UMTS with a Rogers SIM card.

The CDMA radio in a AT&T iPhone could work just fine, but is turned off by the firmware. Since AT&T doesn't have any CDMA roaming agreements its not needed. The only thing that would be needed to turn it on is a Verizon or Sprint firmware load by Apple.

rofred wrote:

The CDMA radio in a AT&T iPhone could work just fine, but is turned off by the firmware. Since AT&T doesn't have any CDMA roaming agreements its not needed. The only thing that would be needed to turn it on is a Verizon or Sprint firmware load by Apple.

Actually, that's not the only thing. The phone's information would have to be loaded into Verizon or Sprint's database. Although both loading the firmware and adding the information to the carrier's database are theoretically possible, in practice, you can't actually have it done.

The CDMA iPhone 4S, 5, 5c and 5s have an active GSM radio. The GSM iPhone have the CDMA radio permanently disabled.

I got my phone in the US and need it opened to our service providers (LIME and/or Digicel) in St. Lucia. I have spoken with personnel from both Verizon and Apple, and they have informed me that the phone is unlocked. I simply have to put in my SIM card and it would work. However, that does not work. I believe that the phone is locked to CDMA but we use GSM in St. Lucia and the rest of the Caribbean. Please tell me if there is ay simple way of changing the network to GSM.

Thanks in advance.

<Email Edited by Host>

What is the exact message that you get when you try to use a SIM?

What does this have to do with the topic of this thread, which is now nearing 4 years old?

Where, EXACTLY, did you get the phone and what reason do you have to believe it's a Verizon phone? In addition, exactly what model phone do you have?