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 a voice call; and in response to the request to establish the voice call: accessing, by the UE, a 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 voice call, whether voice over a packet-switched domain is supported by a first wireless access technology of the plurality of different wireless access technologies, wherein the UE determines that voice over the packet-switched domain is supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a first value, and the UE determines that voice over the packet-switched domain is not supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a second, different value, the device configuration parameter being part of a collection of configuration parameters stored in the UE that relate to a configuration of the UE, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, attempting to establish, by the UE, the 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 a voice call; and in response to the request to establish the voice call: accessing, by the UE, a 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 voice call, whether voice over a packet-switched domain is supported by a first wireless access technology of the plurality of different wireless access technologies, wherein the UE determines that voice over the packet-switched domain is supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a first value, and the UE determines that voice over the packet-switched domain is not supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a second, different value, the device configuration parameter being part of a collection of configuration parameters stored in the UE that relate to a configuration of the UE, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, attempting to establish, by the UE, the voice call over a second wireless access technology of the plurality of different wireless access technologies. accessing, by the UE, a 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 voice call, whether voice over a packet-switched domain is supported by a first wireless access technology of the plurality of different wireless access technologies, wherein the UE determines that voice over the packet-switched domain is supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a first value, and the UE determines that voice over the packet-switched domain is not supported by the first wireless access technology responsive to detecting that the device configuration parameter is set to a second, different value, the device configuration parameter being part of a collection of configuration parameters stored in the UE that relate to a configuration of the UE, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, attempting to establish, by the UE, the voice call over a second wireless access technology of the plurality of different wireless access technologies.