4 Selecting Menu Options.4 Using Your IP Phone with Mitel Unified Communicator Express.4 Usinĥ312/5324 IP Phones User Guide CALL HANDLING.14 Hold. Mitel and its affiliates and subsidiaries assume no responsibility for any errors or omissions in this document. The information is subject to change without notice and should not be construed in any way as a commitment by Mitel or any of its affiliates or subsidiaries.