A method of establishing a call between an enterprise-associated mobile device configured for wireless communications over a public land mobile network, PLMN, and a remote party through an enterprise communications system, the method comprising the steps of: instructing the public land mobile network to forward call requests addressed to the mobile device to an associated enterprise phone number; receiving, at the enterprise communications system, a request from the remote party to establish the call between the enterprise-associated mobile device and the remote party; determining, by the enterprise communications system, that the request comprises a forwarded call request addressed to the mobile device and forwarded by the PLMN to the associated enterprise phone number; and based on that determination, establishing a first call (92, 96) between the enterprise-associated mobile device and the enterprise communications system, wherein when an absence of a VoIP-capable IP connection with the mobile device is detected, establishing the first call includes: sending a data message, for example a SMS message, from the enterprise communications system to the mobile device informing the mobile device of the request from the remote party, wherein the data message is sent via the PLMN, whereby this data message is not a call set-up message of the PLMN; and receiving, at the enterprise communications system, a circuit-switched voice call via the public land mobile network from the mobile device, the voice call being addressed to the enterprise communications system, in response to acceptance of the request by the user of the mobile device, wherein the voice call is placed automatically by the mobile device in response to said acceptance. establishing, by the enterprise communications system, a second call (90, 94) between the enterprise communications system and the remote party, and bridging the first call (92, 96) and the second call (90, 94) at the enterprise communications system to connect the enterprise-associated mobile device and the remote party. instructing the public land mobile network to forward call requests addressed to the mobile device to an associated enterprise phone number; receiving, at the enterprise communications system, a request from the remote party to establish the call between the enterprise-associated mobile device and the remote party; determining, by the enterprise communications system, that the request comprises a forwarded call request addressed to the mobile device and forwarded by the PLMN to the associated enterprise phone number; and based on that determination, establishing a first call (92, 96) between the enterprise-associated mobile device and the enterprise communications system, wherein when an absence of a VoIP-capable IP connection with the mobile device is detected, establishing the first call includes: sending a data message, for example a SMS message, from the enterprise communications system to the mobile device informing the mobile device of the request from the remote party, wherein the data message is sent via the PLMN, whereby this data message is not a call set-up message of the PLMN; and receiving, at the enterprise communications system, a circuit-switched voice call via the public land mobile network from the mobile device, the voice call being addressed to the enterprise communications system, in response to acceptance of the request by the user of the mobile device, wherein the voice call is placed automatically by the mobile device in response to said acceptance. establishing, by the enterprise communications system, a second call (90, 94) between the enterprise communications system and the remote party, and bridging the first call (92, 96) and the second call (90, 94) at the enterprise communications system to connect the enterprise-associated mobile device and the remote party. sending a data message, for example a SMS message, from the enterprise communications system to the mobile device informing the mobile device of the request from the remote party, wherein the data message is sent via the PLMN, whereby this data message is not a call set-up message of the PLMN; and receiving, at the enterprise communications system, a circuit-switched voice call via the public land mobile network from the mobile device, the voice call being addressed to the enterprise communications system, in response to acceptance of the request by the user of the mobile device, wherein the voice call is placed automatically by the mobile device in response to said acceptance. establishing, by the enterprise communications system, a second call (90, 94) between the enterprise communications system and the remote party, and bridging the first call (92, 96) and the second call (90, 94) at the enterprise communications system to connect the enterprise-associated mobile device and the remote party.