I got an email from one of the incoming students at our school asking about cellphones. I have no idea how to answer this question (I don’t even know what a SIM card is!) so I thought I’d seek out some expertise here. 
They’ll need to look at AT&T or T-Mobile as AFAIK, those are the only carriers in the US that use SIM cards. (SIM stands for “Subscriber Identity Module”)
Here’s my off-the-cuff knowlege:
A SIM card is what some phones use to identify itself to the cell network, and is what associates that phone with a given user’s account (and phone number).
I have a co-worker who recently did some traveling in Asia, and while he was there he got a local SIM card so he wouldn’t be making “international” calls when calling Asian numbers. From his description, it sounded like pre-paid SIM cards were available (much like pre-paid cell phones I’ve seen in the US) so people could keep their own phones, and just buy time on the local cell network.
Now, regarding your student, I would assume that he would be able to get a new SIM card for his existing phone if he signed up with a US carrier (Sprint, Verizon, T-mobile, etc). However, I don’t know if “pre-paid” SIM cards are that common. And I have absolutely no idea on what international rates are available.
And on preview, I guess SIM cards aren’t as widespread as I thought (I use Cingular / AT&T, so I knew my phone had one).
Does that offer at least a little help?
A SIM card is used for GSM phones.
There are several cellular phone technologies around. Most of the carriers in the US use CDMA. Most of the rest of the world uses GSM. One advantage to a GSM phone is that your account’s identity (i.e., your phone number) is not hard-coded to the phone, it in encoded in a SIM card, which is a chip embedded in a small removable card a little bigger than a postage stamp. The beauty of a SIM card is that you can take the card out of one phone, put it into another phone, and you’re good to go.
The US GSM carriers use a different frequency than Europe (and there’s a third frequency as well), although some GSM phones can use all three frequencies. If not, you have to put your SIM card into a phone that will work with the local network.
Your student may have acquired a phone without getting an account for it, and needs to set up an account in the US, along with getting a SIM card. Lots and lots of companies offer SIM cards with service, not just T-Mobile and AT&T. They may own GSM networks but they are not your only choices for service. Google “SIM card US”.
One example of such a company is
I used this company to get a SIM card and phone to use in Europe:
http://www.thetravelinsider.info/roadwarriorcontent/mobalrental.htm
Prepaid and pay-as-you-go plans are available.
By the way, whether she uses a prepaid SIM card or a regular prepaid phone , she probably wouldn’t want to make international calls straight from her cell. It’d be really expensive. Once here, she should pick up an international calling card at a grocery store, post office, etc. That’ll get her much better rates.
Once the student gets an international calling card, it would be a simple matter to use the calling card from their GSM phone with their prepaid SIM card. If they’re scrutinizing enough, the cost of an international call might be as little as 10 cents per minute.
Of course, the student’s family could just get a Skype number local to your area in the US. Then, the student would just need to call that number locally from their cell phone and their family could answer from their computer.
If the phone was acquired outside of the US, it is very likely unlocked, as a consequence of the different sales experience in most of the rest of the world (In most countries, you shop for the handset seperately from your provider. In the US, you usually pick your provider then choose from the selection of handsets offered by your provider). Most GSM phones are tri-band phones, which will work in the US on T-Mobile. Quad-band phones are even better. The frequencies of interest are AT&T/Cingular’s 850 MHz and T-Mobile’s 1900 MHz networks.
Prepaid SIM cards aren’t anywhere near as common as in most other countries. You can’t walk into most stores and buy a SIM card. You can, though, easily buy a prepaid package which includes a cheap phone, and use the SIM card in your existing phone and, say, sell the bundled phone to someone. Some small, independent, phone shops do sell prepaid SIM cards which they’ve pulled from prepaid kits from T-Mobile or AT&T/Cingular, the only GSM carriers in the US. Other companies (mobile virtual network operators, or MVNOs) buy service from them, like JOLT, who buys access from AT&T/Cingular.
Prepaid Sprint, Nextel, Verizon, and carriers that operate on those networks (such as Boost, Tracfone, Helio, and many others) won’t help in your student’s quest to get a SIM card, since those carriers do not use GSM networks.
T-Mobile has no problem selling prepaid SIMs without having to buy a bundled phone. Since the parent company of T-Mobile is Deutsche Telekom, the company is perfectly prepared to handle international travellers with existing handsets. Prepaid SIM runs fifty bucks at a T-Mobile store and that includes about thirty minutes of airtime. International SMS is .15/each, that’s your cheapest option of all.
50 bucks for thirty minutes of airtime?!
That’s good to know, but the price is ridiculous, both compared to the rest of the world and what you can find in the US from other sources. You can get some prepaid kits for less than that if you order it from T-Mobile’s website, and you get a phone with it that’s guaranteed to work on the network and can be sold off later. Also, an independent wireless store here in Philadelphia had T-Mobile SIM cards with 150 minutes for ~$30
Unfortunately, T-Mobile’s international prepaid calling rate is horrible, at $1.60/min for calls to most countries (http://www.t-mobile.com/shop/plans/prepaidrates.aspx). A prepaid international calling card, available from practically any convienence store or drugstore, will give a much better international rate over any cellular carrier.
I presume you can top it up with airtime later on. That’s how prepay SIMs work here.
Thanks so much guys. I’m just going to send her a link to this thread.
Hi, I’m the student with the Sim question. Just wanted to say thanks for the lowdown. i had no clue that a sim wasn’t well known in the US. in the middle east, everyone’s just buying a new phone every year, while using the same sim card i.e. phone no.
this helps cos i think i’m getting an idea about this stuff. i think i’ll just do what everyone else is doing and will buy a phone with a service contract. though i really hate the idea of paying the bill… but i’m guessing GoPhones -the pay as you go phones- are going to have high rates -so.
Thanks so much again.
That’s pretty much how it’s done here when you buy a new handset if you have a GSM carrier, your SIM goes in the new phone, but you stay with the same carrier. Many people upgrade every one to two years or so, when their contract runs out and are eligible for discounted handsets and rebates. Few people transfer existing handsets to a new carrier, because the handset are locked to the original carrier and most people don’t even know it’s possible to do it at all, let alone unlock the handset in the first place.
Buying a service contract from any carrier will require a credit check. Since you’re probably not going to have any established credit in the US, you either won’t be eligible for a contract or will have to pay a deposit for collateral. So, you’ll probably be stuck with prepaid service, which as you saw, is more expensive than the equivalent contract service.
Ha, right, yeah I forgot about that. So I’ll just do with the prepaid till then. Thanks, Cleophus. Do you think I could buy one at the airport? I checked at Chicago’s airport’s website and it seems to have those small stores.
How long are you going to be here for? If you’re staying for at least a year (the minimum contract length for most cell carriers), a regular plan ought to be a better deal. Leaving the deposit isn’t that big a deal if you can afford it, since you’ll get it back after a year.
If you’d rather go with prepaid, the rates aren’t always that bad. If you pay enough in advance, the rates can go down to 10 cents a minute or so. The trick is to stay away from the mainstream carriers (Verizon, T-Mobile, AT&T, etc.) because their prepaid plans are complete ripoffs. Instead, go with a company that specializes in prepaid service (like Tracfone, Virgin, or Boost). You’ll get much better rates and comparable call quality. In fact, many prepaid providers simply borrow the big carriers’ networks, so you end up with the same coverage anyway.
I’d be careful about shopping in the airport if I were you… most things there, phones included, are overpriced and targeted to travelers who are basically too much in a hurry to find anything better. Wait till you get out and visit a Target, Best Buy, Circuit City or something similar. They’ll have a big selection of prepaid services that you can choose from.
Actually, I’m sorry, I want to retract the statement “The trick is to stay away from the mainstream carriers (Verizon, T-Mobile, AT&T, etc.) because their prepaid plans are complete ripoffs.”.
I haven’t looked at them in a while and it seems some of them are affordable, if you prepay enough in advance.
Okay, thanks. I’m staying for a year but I don’t think I’ll be able to pay the deposit. So the prepaid sounds better. Thanks a lot for the replies. Much, much appreciated from a somewhat nervous traveller ! 