A method and system for customizing a wireless device's user-interface is provided. During activation of the wireless device for service, the wireless carrier will use an identifier of the wireless device (such as an electronic serial number) as a basis to correlate the device with a vendor of the device and in turn to select a customization package that defines a user-interface corresponding with the vendor. For instance, the user interface can have color schemes, graphics, sounds and other attributes that are similar to the color schemes, graphics, sounds and other attributes that the vendor uses to promote the vendor's services or products. The wireless carrier will then send the customization package (or a pointer to the customization package) to the device, over the air in an activation response message for instance. And the device will responsively adopt the selected user interface as a base user interface.