A wireless end-user device, comprising: a processor; a wireless wide area network, WWAN, modem to communicate data for network service usage activities between the device and a WWAN, when connected to a WWAN; a wireless local area network, WLAN, modem to communicate data for network service usage activities between the device and a WLAN, when connected to a WLAN; a computer-readable storage medium storing instructions that, when provided to the processor, cause the processor to determine, for a first device application whether the application is running in a background state or in a foreground state, and control, via an application program interface, API, application access for network service usage activities provided through the WWAN modem and the WLAN modem, to, based on a first traffic control policy, selectively block and allow access by the first device application to at least one of the WWAN and WLAN modems (1812, 1813), wherein the access is selectively blocked based on a determination that the first device application is running in a background state, and wherein the access is selectively allowed based on a determination that the first device application is running in a foreground state. a processor; a wireless wide area network, WWAN, modem to communicate data for network service usage activities between the device and a WWAN, when connected to a WWAN; a wireless local area network, WLAN, modem to communicate data for network service usage activities between the device and a WLAN, when connected to a WLAN; a computer-readable storage medium storing instructions that, when provided to the processor, cause the processor to determine, for a first device application whether the application is running in a background state or in a foreground state, and control, via an application program interface, API, application access for network service usage activities provided through the WWAN modem and the WLAN modem, to, based on a first traffic control policy, selectively block and allow access by the first device application to at least one of the WWAN and WLAN modems (1812, 1813), wherein the access is selectively blocked based on a determination that the first device application is running in a background state, and wherein the access is selectively allowed based on a determination that the first device application is running in a foreground state. determine, for a first device application whether the application is running in a background state or in a foreground state, and control, via an application program interface, API, application access for network service usage activities provided through the WWAN modem and the WLAN modem, to, based on a first traffic control policy, selectively block and allow access by the first device application to at least one of the WWAN and WLAN modems (1812, 1813), wherein the access is selectively blocked based on a determination that the first device application is running in a background state, and wherein the access is selectively allowed based on a determination that the first device application is running in a foreground state. wherein the access is selectively blocked based on a determination that the first device application is running in a background state, and wherein the access is selectively allowed based on a determination that the first device application is running in a foreground state.