Zoom 3G+ USB Freedom Adapter for AT&T & T-Mobile. With the 4597 Freedom Modem you can be free of long term contracts. The Model 4597 works using the fastest available mobile broadband services from both AT&T and T-Mobile in the United States. With the 4597 3G Freedom Modem you start and stop mobile broadband service as needed, change service providers, or change service plans without incurring a financial penalty. The modem is activated by plugging in a standard SIM card from AT&T or T-Mobile in the US. Both pay-as-you-go and prepaid mobile broadband plans are available. Unlike other modems, the Model 4597 is not locked to a specific service provider. A change to the service provider is accomplished by simply sliding out on provider's SIM an replacing it with another provider's SIM. It takes only seconds. Mobile broadband service pricing, coverage, and speeds are changing at a rapid rate. Prudent 3G users know that an unlocked modem like the Model 4597 gives them the flexibility they need to obtain the best deal available. And if your residence or job changes, the 4597 allows selection of the best service available at the new location.