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.