Using a standard SIM card in your GSM (and some CDMA) BlackBerry is pretty easy to grasp at this point. Most come pre-installed if you buy your device from a carrier store, and even if it isn't, getting it in your phone is pretty straight forward. If you're like me however, you might have a micro SIM you want to use in your BlackBerry (I often use both an iPhone 4 / Bold 9900 and swap SIMs between them) it can be a bit more tricky.
Going forward to BlackBerry 10, the micro SIM will most likely be the card of choice for phones as we've seen in the BlackBerry 10 Dev Alpha already. If you want to use a micro SIM in your current BlackBerry however, you'll need to either pick one up from your carrier or cut down your current SIM (which I don't recommend). You'll then need to purchase a micro SIM adapter. Read on and we'll take a look at how to use a micro SIM card in your BlackBerry smartphone.
Using a micro SIM in your BlackBerry smartphone
Getting started - What you'll need
First things first - you'll need a micro SIM.

We have two choices here, the first is kind of a bold move which I wouldn't suggest trying - cutting down your standard SIM card. To do this, you'll need to have some crazy skills with an exacto knife or buy a SIM cutter.
If you're afraid of cutting up your current SIM card (which you should be!) you can usually get one free from your carrier. Either stop by a store or call them up and they should swap out your current, standard SIM card for a micro SIM.
The next thing you'll need to do is purchase a micro SIM adapter.
Once you have both your micro SIM card and micro SIM adapter, the rest is easy. Now keep in mind things may vary a bit here depending on your device, so take that into consideration.
Putting in your micro SIM
Put your micro SIM into the adapter as seen here. It really only fits one way so it shouldn't be too hard to figure out.

The card will most likely be a bit loose and can fall out easily, so be careful as you slide it into the SIM slot on your device. There is a chance it will get stuck a bit (as it does often on my Bold 9900) so press it down as you slide it in.
Once it's fully inserted into the SIM slide, replace your battery and fire up your device. Make sure wifi is off and test it out to make sure your data is working properly. You'll obviously need to make sure you have a BlackBerry data plan through your carrier for the micro SIM to work, so make sure you have that setup ahead of time (or call your carrier to setup a BlackBerry plan).
That's all there is to it. Now you'll have a micro SIM you can swap between your BlackBerry and other devices, plus you'll be ready for BlackBerry 10!
Purchase a micro SIM adapter from Amazon
robsteve May 15, 2012 at 12:51 pm
There has been a post or two about these adapters catching the pins on the SIM reader and bending or breaking them.
You might also make a note about changing SIMs in an OS7 device can require a BBID login and if you do not have data on the SIM or have a wifi connection established prior, you will not be able to login to the BBID or use the phone. If you fail to login you may need to do a security wipe and start over. This is not something you want to run into when not handy to a computer to restore your phone.
ps4rh May 15, 2012 at 1:07 pm
You can get around that with a bit of scotch tape around the adapter to seal the edges. You'd then cut the tape away around the actual contacts.
It also helps if you can avoid adapters that don't have a barrier at the top.
malwayne66 May 15, 2012 at 12:52 pm
Will CrackBerry be stocking these adapters if/when BB10 starts to use them. Looks like many persons are gonna be switching out micro-sim or "cut-out" sim if BB10 devices start using them
Adam Zeis May 15, 2012 at 1:01 pm
You won't need the adapter for BB10 devices (most likely). They'll take the micro SIM, so the only time you'd need the adapter is if you wanted to use the micro SIM in a standard SIM device (like current BB's)
cgk May 15, 2012 at 1:31 pm
In the UK now, more and more the carriers are simply issuing microsims within a caddy anyway, so no cutting needed.
exnokiafanboy May 15, 2012 at 2:15 pm
This is really a bad idea for BB 9810. I broke my sim card reader pins on a brand new BB 9810. Had to replace the entire motherboard to fix it. Very expensive mistake.
Craigash May 15, 2012 at 2:15 pm
whats the difference, apart from size?
curvezzz May 15, 2012 at 2:50 pm
That's the only difference.
automan69 May 15, 2012 at 2:39 pm
I have the micro sim with adapter and never ran into any problems. I now have the choice to roll and rock between bold 9900/9870 desire,amaze iphone4. Now let's hope I win the Porsche Design P'9981 BlackBerry and I'm all set 6 days a week.
Bold_until_Hybrid_Comes May 15, 2012 at 2:42 pm
IT RIPS THE SIM CARD READER PINS OFF
Rootbrian May 15, 2012 at 4:04 pm
Caps lock stuck? No it doesn't, not if you are careful to insert it.
Bold_until_Hybrid_Comes May 15, 2012 at 7:40 pm
No it was not stuck I wanted to type in capital letters.
Gadberry May 15, 2012 at 2:43 pm
Just so everyone knows if you have a 9900 ,9780,9700 or any berry that has a visible sim slot ( no torches) you dont even need a sim adapter. Just slide the microsim over the contacts and it will work fine. No adapter in my 9900 or the wifes 9700. It might take a couple adjustments to get it to line up correctly but thats the only hassle.
elvin1983 May 15, 2012 at 2:50 pm
Also, I believe AT&T does charge about $30 for a new SIM card. At Sam's Club a new one for AT$T is $7 bucks.
Crypt1c May 15, 2012 at 8:21 pm
If you go to an authorized retailer they will charge $30. However if you go to an official AT&T store you can get a new sim at no cost.
BionicKris May 15, 2012 at 11:42 pm
I got a new one recently at my local AT&T store and it was free
Bold_until_Hybrid_Comes May 15, 2012 at 7:41 pm
In canada I do not think SIM cards are free?
robsteve May 15, 2012 at 8:13 pm
My wife just went from an iPhone 4s to 9810 and a new regular size Bell SIM was $5.
zensen May 15, 2012 at 8:18 pm
these micro sims are such a pointless move into pointlessness.
pringler May 15, 2012 at 10:55 pm
I have been using a uSIM for the past year in all of my BlackBerry phones? You dont need an adapter lol. Just line it up perfectly. I will admit that it did once take me half the morning trying to line it up correctly in my 9810.
Morjesta May 21, 2012 at 5:41 pm
i been using a micro sim card on a Galaxy S II for 6 months as shown on this post without any issue so far. i think it would work the same way on a BlackBerry.
Mario Lopez2 Jan 23, 2013 at 9:43 pm
cheap adapters will destroy your phone, I bought a good one from Future shop in Canada, I am happy with it.