Which carrier do I have?

[jmeinc22]

I just bought a 8100 off of e-bay, it was suppose to be an ATT phone. However when I put in my sim card it reads invalid card. There are no marking on the phone to tell me who the carrier is and no logo at start up. Is there any way to find out with network this phone is on?

[MobileMadness002]

The carrier is the one you give money to.

If it has no carrier logo at startup then it is unbrabded.

Here's your sign.

[californiablackberry]

What happens when you turn the device on? There should be a carrier start-up animation.
If it just says RIM, it's unbranded.
Which model did you purchase?

[blackberry-unlocking710]

you can try to unlock it (without using a code) a step before you will see "network active" ... if you see this it's locked - then you can try to unlock it - if you will get a code then your problem is solved because it will work, if not - then it's unbranded

[x Nadzy x]

I hate to be the bearer of bad news, however, if no sims work then your phone is blocked. This is where you cannot calls or text and can be rarely fixed, but it is illegal.