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 ...

In the company’s earnings report on Thursday, Verizon Wireless revealed that it activated 2.2 million iPhone 4 units in the first quarter of 2011. While AT&T reported earlier this week that it ...