Lately Ive been receiving a lot of questions and comments on the issue of AT&T vs. T-Mobile SIM cards. So I decided to write up a little info on this issue to hopefully help clear things up a little.
[Note: This information applies equally to TracFone and Net10 users. However, to make for easier reading, I'll be referring only to "TracFone." If you're a Net10 user, just replace the word "TracFone" with "Net10."]
For those of you who don’t know, TracFone don’t own any networks – they just contract with the network owners, or “carriers,” to use the networks. There are three main carriers that TracFone works with: AT&T, T-Mobile, and Verizon (who now also owns the former Alltel network). The former two carriers operate “GSM” networks, while Verizon’s network uses the “CDMA” standard. For more information on these two technologies, check out my old TracFone CDMA vs. GSM article here.
Here’s a simplified view of how the GSM phones work on TracFone: The GSM carriers require that each phone use a “SIM Card.” In the case of TracFone GSM phones, you will get a SIM card that is native to either the AT&T or the T-Mobile network. The type of SIM card determines which network your particular phone will give preference too, in case both networks are available.
For example, if you have a T-Mobile SIM in your phone and you’re in an area where both AT&T and T-Mobile networks are available, your phone will use the T-Mobile network. If you travel into an area with only AT&T coverage, you should be able to use the AT&T network. However, this is where things get a little murky for TracFone users.
Throughout the comments on this blog and on other forums around the web, TracFone users with T-Mobile sim cards in their phones have reported subpar or even unacceptable roaming ability. As far as I can tell, these problems seem to arise when a phone with a T-Mobile SIM is in an area with a strong AT&T signal, but weak T-Mobile coverage. Since the T-Mobile SIM tells the phone to give preference to the T-Mobile network, that’s the network you’ll be forced to use – even though the AT&T signal is stronger.
This issue is compounded by the problem that AT&T has a more comprehensive network, so it’s a fairly common problem to use an inferior T-Mobile signal when AT&T would be a better option. Further, users with T-Mobile SIM cards have also reported problems with the data capabilities of their phones, having trouble sending MMS messages and using the mobile web.
Add all these factors together, and the result is that for many (but not all) TracFone users with T-Mobile SIM cards, an AT&T SIM would actually provide better service. On Friday I’ll follow up with another article on this topic, discussing how to tell what type of SIM card is in your phone, whether you should replace your SIM card, and how to make sure you get the SIM card you want when buying a new phone.