A method comprising: receiving , by a user equipment, UE , that is able to use a plurality of different wireless access technologies, a request to establish an outgoing voice call; storing a device configuration parameter in a storage medium of the UE , the device configuration parameter dynamically configured by a mobile communications network; setting a value of the device configuration parameter to one of a first value and a second value responsive to a message received from the mobile communications network, wherein the device configuration parameter when set to the first value indicates that voice over a packet-switched domain is supported by a first wireless access technology, and the device configuration parameter when set to the second value indicates that voice over the packet-switched domain is not supported by the first wireless access technology; and in response to the request to establish the outgoing voice call: accessing, by the UE , the device configuration parameter stored in the UE , determining, by the UE , based on the device configuration parameter accessed in response to the request to establish the outgoing voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, initiating establishing, by the UE , the outgoing voice call over a second wireless access technology of the plurality of different wireless access technologies. receiving , by a user equipment, UE , that is able to use a plurality of different wireless access technologies, a request to establish an outgoing voice call; storing a device configuration parameter in a storage medium of the UE , the device configuration parameter dynamically configured by a mobile communications network; setting a value of the device configuration parameter to one of a first value and a second value responsive to a message received from the mobile communications network, wherein the device configuration parameter when set to the first value indicates that voice over a packet-switched domain is supported by a first wireless access technology, and the device configuration parameter when set to the second value indicates that voice over the packet-switched domain is not supported by the first wireless access technology; and in response to the request to establish the outgoing voice call: accessing, by the UE , the device configuration parameter stored in the UE , determining, by the UE , based on the device configuration parameter accessed in response to the request to establish the outgoing voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, initiating establishing, by the UE , the outgoing voice call over a second wireless access technology of the plurality of different wireless access technologies. accessing, by the UE , the device configuration parameter stored in the UE , determining, by the UE , based on the device configuration parameter accessed in response to the request to establish the outgoing voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, initiating establishing, by the UE , the outgoing voice call over a second wireless access technology of the plurality of different wireless access technologies. <EOS>