In order to use the phone parts of FONA you will need a SIM card. Luckily, there's a phone store in every town in America! You can get a pre-paid or post-paid SIM but we kinda like the pre-paid kind.

A 2G Mini SIM card is required to use the module. Nearly any cell phone shop can sell you a SIM card. It must be a 2G GSM card. AT&T in the US does not sell these anymore! They are shutting down their GSM network, and only T-mobile sells and supports a GSM network. If you are in another country, chances are you can just ask for a GSM 2G card.

MicroSIMs won't fit - so make sure its a "Mini" SIM. Sometimes these are just called plain "SIM" cards since the huge-size SIMs are rarely used. Mini SIMs are 1" x 0.6" / 25mm x 15mm. these are by far the most common size.

The only thing to watch for is you need to have a 2G GSM-compatible SIM

If you have an older AT&T SIM it may work. AT&T announced in 2012 that they would shut down their 2G network January 1, 2017. The vast majority of M2M (machine-to-machine) cellular devices use GSM, so the 5 year lead time was to give people plenty of time to migrate from AT&T.

You can read an interesting whitepaper from Aeris about this below:

T-Mobile & TING

T-Mobile does not have any announcement that they will sunset GSM. We can't speak for them but we expect at least 5 years warning as well, probably they will never fully sunset since there's millions of machines with GSM connectivity.

Adafruit now sells the TING SIM card, a 2G GSM SIM that works great with all FONAs, and has a great billing system as well, where you only pay what you use!

If you don't want to use TING, there are dozens of T-Mobile resellers such as Walmart, SIMPLEMOBILE, etc! Just ask the seller if its AT&T or T-Mobile network. If they get cagey just say your apartment has no AT&T coverage.

Some suggestions from FONA users!

• I've had good luck using the FONA with a SIM from Walmart. Their 'Walmart Family Mobile' is a T-mobile reseller and you can pick up the SIM starter in store pretty easily . The service isn't the cheapest, it's $25 for the SIM and $30/month for unlimited talk+text or $40/month for unlimited talk+text+data but there's no contract as its all prepaid -tdicola
• Just want to let the Adafruit team know that it is possible to get pre-paided minutes on T-Mobile and its a pretty good deal. I was paying $100 for 1000 minutes (10c a minute 20 a sms) over the course of the year. For me it in my usage came out to about $8 a month. Have found this is something that you have to ask for at the store. No evidence in advertising or website -Paul B.
• Telna has a good deal you may want to point people to for FONA. I used them for a previous GSM project and they worked great. $20 per year, includes 1000 free txt messages and a bunch of other nice features. I had a lot more issues with T-Mobile (Their cards go inactive if not used in a month and you have to call to reactivate) -Tyler C.
• I pay 2 EUR (a bit less than $3 USD) for 2 hours, unlimited SMS and 50Mb of Data at http://mobile.free.fr/ -KTOWN
• There are specialty "machine 2 machine" SIM sellers that have plans that are tuned for the short bursts of usage used by these kinds of modules. Check out these guys for example, you can choose data, voice/sms or a combination for a pretty low price!
• Hi, just a update to let you know I have just begun to use the Fona, SIM from ROGERS, which is 2G, 3G, ang 4G. I pulled my sim out of my phone, and it works well. So if you have Canadians that want to use that product, let them know it works on the west coast ! You can go to Rogers website and see the coverage map and services. - Steve C

We haven't tried all of these SIMs so you may need to try it out. For other countries, GSM is very common so you should be able to buy a SIM from any cell phone store.