Here's everything you need to know about the activation process. Activate your Cricket SIM in a few simple steps A SIM ...

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.

Sometimes you might not be able to use Airtel 4G on your 4G ready smartphone. In this case, the problem can be with your SIM card. It only means that you are still using only 2G or 3G SIM.

Several users reported spending hours at their local T-Mobile store trying to activate their new SIM without recourse. Since the activation process disables the old SIM, users are stuck without ...