ST SIM for unlocked phones: how is it decided whether AT&T or T-mobile is used?

**Steven222** · 06-08-2012, 06:06 PM

Hello,

I'm considering ordering a Straight Talk SIM for an unlocked GSM phone, but I'm confused about how it's decided whether ST's unlocked-phone SIM will use AT&T or T-mobile service. If I order the SIM for unlocked phones (as opposed to ordering one of the carrier-specific SIMs), does the phone take advantage of both networks? If so, how does it decide which carrier to use at any given moment? Would it be simply be based upon relative signal strength? What about if one network has a stronger signal, but still has slower data in that particular area?

Or is it that if I order the unlocked-phone SIM, that Straight Talk chooses the carrier for me at the time of my order (based on my zipcode or some other factor) causing my phone to use one carrier as if I had ordered the SIM specific to that carrier? If that's the case, who would order the unlocked-phone SIM?? If your phone is to operate on only one network, wouldn't it always be better to make the AT&T vs. T-mobile decision yourself, rather than having ST make it for you?

Straight Talk's website isn't real clear as to how it's decided which carrier one's phone will use if you order the unlocked-phone SIM. Any info to educate this newbie would be appreciated. Thanks!!

Steven

**Redking117** · 06-08-2012, 06:17 PM

There is a T-mobile sim and an AT&T sim

The T-mobile sim uses T-mobile towers the AT&T Sim uses AT&T towers

You decide which one to buy, see who has the best service in your area.

the only way you will be able to roam is if you had to call 911...

**alphamale-b** · 06-08-2012, 06:39 PM

it may be a matter of their cost. if tmobile is cheaper and you dont declare an att sim well you get whats cost effective for them. mr slim is very rich and you do not get that way by accident usually.

**Steven222** · 06-08-2012, 07:27 PM

Originally Posted by Redking117

There is a T-mobile sim and an AT&T sim

The T-mobile sim uses T-mobile towers the AT&T Sim uses AT&T towers

You decide which one to buy, see who has the best service in your area.

the only way you will be able to roam is if you had to call 911...

Looking at ST's website, there is a T-mobile SIM, there is an AT&T SIM, but there is also a third SIM described as: "Unlocked GSM Phone (Phone must operate in 850 and 1900 MHz bands)." I'm trying to figure out what service (AT&T or T-Mobile) is used if I order this "Unlocked GSM Phone" SIM. Are you saying that if I select it, ST will simply send me their choice of one of the other two (AT&T or T-mobile) SIMs?

**Ric** · 06-08-2012, 07:44 PM

850/1900 are the AT&T bands. And if you step through the buying process they tell you at the end that you will receive an AT&T SIM. At least that's how it came out for me when I put in my zip code.

I don't know why they offer that as a third option. Maybe there are some people that can't make a choice.

Sent from my SGH-i667 via the HowardForums WP7 App

**maestroteague** · 06-08-2012, 10:34 PM

Originally Posted by Steven222

wouldn't it always be better to make the AT&T vs. T-mobile decision yourself, rather than having ST make it for you?

Yes, your instinct is correct. It is better for you to do your own research and ask friends and acquaintances which network works best in your area. If you choose "unlocked", then they will choose for you. We don't know their exact criteria for selection - coverage in your zip code, cheaper price for them, etc. in general, AT&T's network is more extensive, important if you travel a lot. But in areas where tmobile coverage is good, their data speeds are better, and their data is probably less expensive for ST, so they may be more lenient in your data use. So, as in real estate, the answer is location, location, location. Best to do your own research for your are and choose appropriately. Of course, this is only applicable if you nave a phone that is unlocked and has all the bands for both networks. Most people are going to buy a phone that is locked to one or the other of the two carriers, and it is of course best for them to get the sim with that corresponding carrier. Then again, some people tak an AT&T iPhone on tmobile knowing that they will only get edge speeds because the iPhone doesn't have the right bands for tmobile's HSPA+. But beat if you decide rather then letting them do it for you.

**maestroteague** · 06-08-2012, 10:39 PM

One more thing- on the BYOD sim program, you do roam to the other carrier, and to many local and regional carriers. But you only do so when there is no signal from any tower of the primary provider. For instance, I have the AT&T sim. If I'm in a place that has lousy AT&T coverage and has good coverage from tmobile, or one of the other regional carriers the ST has roaming agreements with, then I will not roam onto one of those as long as I have any signal at all from AT&T towers. If have 5% signal strength from an AT&T tower but 90% from tmobile, I'm out of luck. When I get to no signal from AT&T, then I will roam on voice and text to the other provider. Seome of the regional carriers also roam data, but not all of them.

**momto4boyz** · 06-11-2012, 02:21 PM

In regards to the unlocked gsm sim vs att or tmobile, ive been on the phone with straight talk and apple most of the day trying to figure out how to get my mms to work, i know unlock it works for my data. They informed me that i should NOT have purchased an att compatible sim i should have purchased the gsm sim for unlocked phones. they said that is the reason I dont have any way of changing my apn so my mms works. anyone know if this really is true. I dont want to spend more money on another sim card if there just gonna send me another ATT sim since the one i have doesnt allow me to use data or mms.

edit... Opps.. forgot to add i have an unlocked iphone 3g

**funkd00biest** · 06-11-2012, 04:12 PM

ha yeah...I'm willing to bet you would get the same at&t sim you already have. If you choose unlocked sim and add it to your cart during checkout you will see that its changed to an at&t sim.
Are you jailbroken? If so you need to install Tetherme in Cydia and then after that you can go into network settings on iphone edit cellular data and actually edit the APN settings yourself to get MMS working.

**momto4boyz** · 06-11-2012, 05:09 PM

My phone is just unlocked not jailbroken. I had att unlock it. I have a sim card that will show me the apn settings but when i swap them back the settings dont stay.

**funkd00biest** · 06-11-2012, 05:19 PM

Try to do the sim card swap with the 'edit cellular data' settings still up on the screen. That way you can try to edit them again after swapping the sim card. If that doesn't work you may want to look into jailbreaking the iPhone so you can edit the settings with the straight talk sim in the phone.

**momto4boyz** · 06-12-2012, 04:35 AM

tried again, i got to the cellular data screen swapped card back to st sim, put all the info for the apn back in and its gone. ugh!!!

**maestroteague** · 06-12-2012, 06:41 AM

There are several threads with the information you need. First, the rep is completely wrong, which is sadly often the case. If you choose unlocked sim, they will send you either the att sim or the tmobile one. Ther is no actualy unlocked sim. There are 3 ways to change that information in the APN. First is sim swap, which doesn't appear to be working on the 3G. Seconde is to jailbreak and install tetherme. This is the route I took on my 4S, and found it to be very simple. The last is to use a few programs on ur computer to backup your iPhone, edit some data in text files in the backup, then restore the files back to your phone. It isn't terribly hard, but don't know if I'd recommend it to someone who isn't tech savvy. For info on that, look for a thread with the title something like MMs working on I hone 4 without jailbreak. There's also a thread that says step by step setup with iPhone 3G or 3GS (can't remember which).

**momto4boyz** · 06-12-2012, 01:34 PM

thanks for you help, im gonna try to locate those threads.

**Redking117** · 06-13-2012, 03:15 PM

Originally Posted by maestroteague

One more thing- on the BYOD sim program, you do roam to the other carrier, and to many local and regional carriers. But you only do so when there is no signal from any tower of the primary provider. For instance, I have the AT&T sim. If I'm in a place that has lousy AT&T coverage and has good coverage from tmobile, or one of the other regional carriers the ST has roaming agreements with, then I will not roam onto one of those as long as I have any signal at all from AT&T towers. If have 5% signal strength from an AT&T tower but 90% from tmobile, I'm out of luck. When I get to no signal from AT&T, then I will roam on voice and text to the other provider. Seome of the regional carriers also roam data, but not all of them.

Good to know maybe I will switch to my wife's BYOD sim form my E71 sim since her iPhone took a swim in the toilet.