Expert: DebiN - 8/22/2009

Question
QUESTION: Basically, are all cell phones compatible with all cell phone carriers? Seems that every time that a person changes to a different carrier, that new carrier will say that your old cell phone is not compatible with them. The new carrier will say that you have to purchase a cell phone from them, without even looking at what kind of old cell phone you have.

ANSWER: All cell phones are NOT compatible with all carriers. Not by a long shot. There are GSM carriers and CDMA and iDEN carriers and these are three completely different networks and the phones that work on one do not work on another. Additionally, all carriers lock their phones to their networks. In the US, this is how it is done today. Outside the US, people pay a ton of money for phones and most carriers outside the US are GSM and you can use your phone on most networks. But in the US, the carriers subsidize the cost of the phones, i.e., you basically get them for free or little charge, in exchange for a 2 year commitment. By the carrier providing you with a phone, you give them yout commitment for 2 years and then when your contract is up, you can continue with that carrier and get another new free phone or go to another carrier and get a free phone from them. I personally don't think that people in the US would like to have to pay full price for their phones just so that they could change carriers on a whim. In addition, the US carriers charge much less than non-US carriers. Many of the carriers outside the US offer prepaid plans. These are MUCH more expensive than what we do in the US. A free phone and a low cost post-paid plan is by far superior to an expensive full price phone and prepaid minutes. The whole reason that all this unlocked phones being available on line started was for NON-US folks who pay a lot for phones. For those of us in the US, it's silly actually. It's actually more trouble than it's worth to have to program a cheaply made phone that has no warranty and will likely break and have to be replaced when you could have gotten a free phone from your carrier that is under a 12 month warranty, can get insurance on it and don't have to worry about things working. I hope this helps. Thanks. DebiN

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QUESTION: Thank you for writing. Your response helped alot to clarify things. Recently, my sister changed to a family plan and brought me on to her account with AT&T. I used to use T-Mobile. AT&T said that my T-Mobile phone is not compatible with the AT&T service.

The way I unserstand it from your response is that AT&T and T-Mobile are both GSM carriers. So why is my T-Mobile phone not compatible? In addition, my sister and I don't use text messaging or the email features (in case this makes a difference).

Also, one time (several years ago) I purchased a blakberry from Wirefly.com (on a rebate), and Wirefly programmed it for the carrier that I was using at the time.

If I understand your response, within the United States, the US used to be able to use any phone with any carrier but not any longer?


ANSWER: Your T-Mobile phone is locked to T-Mobile's network and can only be used with a T-Mobile SIM card. If you had someone SIM unlock it, your AT&T SIM would work in the phone, but only for voice and text and would need to be programmed for AT&T's MMS and WAP.

When you bought a phone from Wirefly, they programmed a GSM phone for the settings for the carrier you selected. You would not have been able to have them program a CDMA phone for a GSM carrier or vice versa. The phone had to be compatible with the carrier's network to start and then they programmed the MMS and WAP settings for the carrier.

In the US, we have never been able to use all phones with all carriers. Since cell phones first came onto the market, each carrier has locked their phones to their networks and there have always been at least three different networks types being used. AT&T and Verizon have never used the same network type (before GSM, AT&T used TDMA while Verizon was CDMA). Even in their earlier iterations, it was like this. Nothing changed in the US, you have always had to have a phone branded or coded to your carrier. I hope this helps. Thanks. DebiN

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QUESTION: So it all boils down to the SIM cards and which carrier the SIM cards are programed for?

Thank you so much for your help!

Answer
In the case of GSM phones, it is the phone itself that is SIM locked to accept only a that carrier's SIM card. In the case of CDMA (like Verizon and Sprint), the phone is locked to only allow activation for that carrier's ESN numbers. I hope this helps. Thanks. DebiN