Why doesn't my iphone work with my at&t sim card?

[ulisesg]

i bought an iphone and let my friend borrow it so he could jailbreak it and unlock it to use it on tmobile but he couldn't do it, but when i put in my at&t sim card it doesn't read it, it just has 5 dots where the bars should be. I think all i have to do left is install the yellowsnow application from cydia but it won't let me connect to it via wifi either somebody please help me

[Unregistered]

To which network is your iPhone locked with?To unlock an iPhone remote unlocking method is the best method. You can get the unlocking service from network provider, sometimes they deny. In that case you can get the remote unlocking service from trusted third party like Classicunlocking.com and follow the free unlocking instructions to easily unlock from the locked network.