You can activate your AT&T SIM in-store, online, or by contacting customer service. The process is similar for postpaid and AT&T prepaid customers.

Make sure you're eligible to change your number First, make sure your account and cell phone are eligible for a new number. If you're still within 30 days of your initial activation with AT&T ...

All you potential iPhone 3G buyers who loathe the thought of having to go into an AT&T store to activate your newly purchased phone can rejoice today as AT&T has finally enabled home activation ...

AT&T has cut $50 off the price of the iPhone 4, making the total price with new two year activation just $99 for a 16GB unit. If you’re alright with taking one with a “cosmetic blemish,” you ...